There's a lot of spiritual and new-age material on the power of "positive thinking". Many will swear that it works, some will even say that it is life-changing for them. Others will say it's new-age mumbo jumbo that doesn't do much.
So... what's the truth? Does it work or is it a failure?
How can there be such a difference of opinion?
The short answer is that it depends on the individual. It's like quantum phenomena that are dependent on the observer.
The longer and more complicated answer is that what we experience seems to be happening at 2 layers. The first is our mind. The second layer is our ability to affect reality - or better stated "choose" a reality.
Layer 1: The mind
Let's start with an example: If one believes they are lucky, their subconscious will be leading them to choices that are aligned with this belief. If one believes they are unlucky, their subconscious will be bringing them "misfortune".
Positive thinking, as a solution to one's problems, is usually suggested when someone is already in a problematic frame of mind where the world seems a darker place. "Think positive and maybe things will change" - we hear. This is similar to being "hopeful".
Both "hoping" and "thinking in a positive way" (just in case things change), represent subconscious admissions that the bad outcome is what we are really expecting. Thus our primary belief is one of a bad outcome - and not a positive one.
Positive thinking is not about wishing away the bad outcome all the while sublimely fearing it will happen.
The mistake people make is confusing what they want, with what they really believe. The subconscious is led by what we believe, not by what we want.
Layer 2: The mechanics of shaping reality
This reality is very malleable and personalized based on our expectations. The interaction of the "observer" with "reality" is like a room of mirrors. It reflects the projections of those walking inside it. The mirror mechanism works by us "tapping" one timeline, out of an infinite number of parallel timelines, where what we've "chosen" through our beliefs, is reflected back at us as the most matching reality.
Our "projections", in this case, are our sublime / subconscious expectations of what will happen. These are not to be confused with what we consciously state that we want.
Now, if we are in a situation and we expect something positive, then it is more likely that we'll get a positive outcome.
Someone might ask at this point: "Why do you say likely? Why doesn't it ALWAYS work?"
The answer to that introduces further layers of complexity: Apparently we also have "blanket beliefs" and "blanket expectations" on how the world operates.
A blanket belief could be that "God dictates things", "Fate dictates things", "Randomness dictates things", "Causality determines things", etc etc.
In the cases where people believe in a more random universe, or in cases where they allow the possibility of external sources of "intervention" (like "God", "saints", "higher self", etc etc) - these will tend to mix with other beliefs, thus creating multiple simultaneous expectations that may conflict between them.
It's like "I think this will happen, but hey, life is full of random events - anything can happen". So at that point, the expectation of randomness, introduces such.
Or another could say "I believe I'm headed for a negative outcome but I have faith in God because he has saved me so many times in the past". That would also introduce "uncertainty" due to the multiple conflicting expectations.
In the end the belief that one believes most, will win. Reality creation mechanics are like Newtonian physics, in a sense:
A helicopter may weigh 2 tons and need 2+ tons of lift to start hovering above the ground. So you have competing forces (+2 tons of weight / -2 tons of lift). The moment the lift is more than the weight = you get an increase in elevation The moment the lift drops to a level below the weight = you start losing altitude.
The sum of beliefs determine the outcome
So the real question that will answer whether the result will be positive or negative, is:"what do I really believe will happen in the end". If one can't answer that, then they can ask "what is the sum total of all the conflicting beliefs I hold?"
Finding all the conflicting beliefs will require increased awareness, because some of these are taken for granted - like one's world view on things like "randomness", "divine intervention", "causality", "luck" etc.
Other beliefs are subconsciously implied by how we envision our future.
If, for example, the way we see ourselves in a week, a month, a year, five years, is more-or-less similar to what we have right now, that's an implied belief that things won't be changing much to any positive or negative direction.
Interestingly, some times a psychologist will ask the patient "where do you see yourself in 2-3-5 years". The answer to that question is very revealing of one's belief system and it can create an outline of one's frame of mind that may be blocking one from progressing relative to a certain problem they face.
Obviously, the implied beliefs created by our vision of the future are not necessarily the only ones that will manifest because there are more beliefs in the "mix". And the "mix" will create the sum total. In the end, the sum of all our conflicting beliefs will determine the outcome.
Speed of manifestation
Some say that if you believe something strong enough it will happen very soon. In my experience, this is not the case. Manifestation speed is not related to the strength of the belief. Manifestation is always INSTANT - even if misunderstood. Most people are simply manifesting delay (and doing so ...instantly).
Now, on a practical level, what people actually mean is whether, for example, one can win the lotto in a week or a year. So the rationale expressed is that if one believes it "more", they'll get it faster. Again, in my experience, this is not the case. What matters is twofold:
1) What timeframe do we consider realistic for the manifestation of a certain possibility: If we ask ourselves then we will usually get a feel for the answer on that. If we don't get the feel, we can phrase it like this: "Can I be a multi-millionaire in a week?" If what I really think is "no", then the answer is no.
Now, if I ask "Can I be a multi-millionaire in a year?", at that point it seems more realistic... so due to being more realistic I can believe it more strongly. But the answer can still be "no" in terms of whether I really believe it will happen - even in a year.
2) Lack of conflicting beliefs: The lack of conflicting beliefs is the shortest route towards instant manifestation.
People will be able to notice this when they are generating vague thoughts in their thought stream and then have things happen right there and then. This is also why the "evil eye" phenomenon "requires" the knocking of wood.
"Knock wood" is simply a reminding process. It could be anything else, like touching our nose. It doesn't hold any real meaning. It's just to remind us that we made an UNCONTESTED (0-conflicts in terms of other beliefs) negative thought about something and we don't really want it to manifest.
So we created a process to remind us when we generate uncontested negative thoughts. Once we are reminded of that, we become more conscious of that thought and say "yeah we don't want this to happen".
By our mere awareness of the fact that we generated an uncontested negative thought, we are then initiating a process of sublimely remembering and re-introducing our programming of blanket beliefs as bigger factors that affect our reality. Blanket beliefs like the "natural order of things", "randomness", "physical causality", etc. In this way we feel safer that all those other perceived mechanisms are ...more responsible for what is happening in the world, not us, and so we will cancel out our prior uncontested uni-directional thought by contesting it with more "believable" beliefs.
Now, the speed of manifestation in unidirectional and uncontested thoughts can be frightening for some, even if they are positive in nature. Our dream reality shares similar characteristics of instant manifestation because the "character" we are "embodying" in our dream does not have conflicting blanket beliefs or other expectations. You think something, you get it right there and then. The mechanics are similar - but the speed appears faster there. In new-age-speak this is attributed to "density", with the "astral" being considered "less dense" and thus being able to offer instant manifestation. But it has nothing to do with density really - it's more about conflicting beliefs, or, more precisely, their absence.
Ultimately, most humans would be extremely frightened if they felt they had the ability to instantly create anything that they were thinking. Thus, in order to protect themselves they have to limit their perception of what they are able to create. They need to believe that instant creation is difficult, otherwise they could be manifesting deadly or catastrophic things.
The mechanisms of multiple conflicting beliefs and the expected delay of manifestation are just ways with which we keep our instant creation in check. Or so we want to believe. Because even that is "virtual": We are still ...instantly creating these perceived delay mechanisms, so the 0-delay relation between consciousness and reality is never really cancelled (nor can it be cancelled).
Conclusion
Positive thinking cannot work based on what one wants to happen. What really matters is what beliefs one has in place and what one's expectations are. Does one really expect a positive outcome? If the answer is yes, one's chances are far higher. If one's answer is no, then there is no real positive thinking involved.
Most cases of "positive thinking" fall into the second category where people are actually expecting a negative outcome, yet they think they are practicing "positive thinking". Naturally, the result will fail them.