Love the discussion!
What I meant by 'the mind mastering them'... is yes you're right, the positive and negative thoughts 'begin' in the brain, but what is causing them to be positive or negative? The subconscious mind right, and what caused them to originate there in the first place? That's what everyone as an individual needs to determine, as the subconscious is what wires their 'positive' or 'negative' thoughts, and usually originates from some point in their childhood. Awareness is the first step and sometimes as individuals it's hard for us to remember or know which memories from our childhood caused the various 'barriers' to form.
Our mind is like a computer, so if we don't take the necessary steps to understand it and start to wire it ourselves, it will in a sense control us.
And yes of course, the environment is a major factor to one's state of mind, especially when it is in a vulnerable state. However one must get to a point where they are able to be in any environment (not necessarily 'stay' there) and still maintain their mastered mindset.
I love that you're encouraging your family member. I struggled with clinical depression for 10 years and that spiral is a horrible experience. I wish all the best for him/her and your family - if he/she agrees, try and get him/her to see a life coach or someone who is able to pinpoint when the barriers formed and work through them together. Life coaches are amazing as they give the individual the tools to free/empower themselves. They also don't necessarily 'diagnose' and put people in boxes like most western practitioners (who aren't holistic enough in the first place), nor do they try and treat the problem by masking it with external pills.
RE: DELETE