This is a tricky sentence. Although I do believe in it, I don't believe in it. Thanks to 
How to motivate people? With words, actions and repetition than convinces them that they CAN! And when they can, most will eventually also do.
Yes you can!
Just do it!
But they should remember that just because they can, doesn't mean they are any good.
First of all, there are always people who love what you do and also people who hate everything you do. That's something you can not change. Especially if you are an artist, you know this to be true, but this also applies to other areas of life. There are always people who adore you and think you have skills and then there are always people who do not like you or what you do, no matter how you do it. You just have one of those faces that repel certain kind of people. Just because you can, does not mean you're any good means that you should do what you want and do it from your heart, train yourself and remember that you can't make everyone like you. So the sentence works as a reminder that if you have your head in the clouds, you should also keep your feet on the ground. Flying in the air suits for birds, bats and bees (and other similar living things that have wings) and cockiness suits only to roosters.
Are you one of those who live by this motitruth? Do you think that you never do anything right. Or the things that you do, are no good and no-one likes you. You have pounded this sentence into your head.
You should stop.
Immediately.
Because it's not true.
Besides feeling sorry for yourself, thinking that you equal shit or that everything you do is bound to fail, is unattractive. And by all means, if your goal is to be unattractive, be that. Do that. Say discouraging things to yourself. Then there's at least one thing you did right. But if your goal is not to be a failure or repel people away, stop thinking you're no good because of the power of self-suggestion. The thing you repeat yourself most, becomes you.
On the other hand if you are the opposite of that person who I described in the previous paragraph, you might sometimes want to tone it down a bit. You can get somewhere with a bit of inherited talent and with enthusiasm, but if you are not willing to work for it, hard, to repeat what you already know, to explore new ways, to learn more and to adjust what you are doing when you realize you have done things wrong or people have lost interest in you, you probably aren't that good. There's that certain age when you stop being cute and start being just embarrassingly sad. So those people who are not your supporters, who do think and say it out loud that you aren't any good, start listening to them. A bit. You don't necessarily have to listen what they say, but why they are saying it. Could they be right? Could you be better? Could you do things better? Or should you just stop.
This is an excellent sentence to remember, but not to live by. And not to be said to anyone. Ever.
Which brings us to the next motitruth.
Family is the first that should be saying to you that you ARE any good, from the fist day of your life to the last. Also when you are not that good, they should be the ones to break it to you gently that perhaps you need more practice and experience. You can find a perfect example of ultimate support in the movie Florence. A true story. --> Florence Foster Jenkins
But if family is just a word for you, it may be that blood relations or people married to your family, mean nothing to you. Unless they prove their value to you. What ever that is that you value. It may be that you value support and encouraging words. But it may be, that you do not get that from your parents. Do you value honesty? It may be that you do not get that from your siblings. Or perhaps you have really high standards and expectations and you want to live your past youth through your children and you think nothing is good enough. Your children just keep on disappointing you. So you think family sucks and that family is just a word, nothing more.
Then you have probably said: "Just because you can, doesn't mean you're any good", or something similar to them couple of times. When you should have said encouraging words, you have put them down. When you should have loved them as they are, you have told them how terrible they are in every way possible. And that they could never be any good, no matter how hard they try. Family is just a word.
Or perhaps you never say to them that they are good or bad. They just are. 'Cause family is just a word.
But you should know, not saying anything is also saying something. Saying something, when things need to be said, is as important as knowing when to close your mouth and swallow the words you want to say. Because family may be just a word for you, but not to your family.
Maybe you would want the word family to mean more to you? You have a family, but you do not want to be part of that family what you have. Then you can forget the blood relations and decide who you want to include to your family. People you trust, people you love and people who support you. Then the word family has a new meaning and it no longer is just a word.
Family may be just a word, but you decide who your family is.
Can't wait what I have for you tomorrow. As it is Valentines and a special day for some. I haven't got the faintest what I'm going to publish, but I'm sure we will all find that out soon and I assure you, I will be just as surprised as you will. :D
Tomorrow.
Just because I can, does not mean I'm any good!
P.S.
Couldn't fit this last thought about the "just because you can" -thing anywhere, so I'll just leave it here. It's a bit stretched on the grammatically correct scale, but so are most of my posts.
Okay so one way to understand "Just because you can does not mean you're any good" is thinking about the thing someone did. Is it a good or a bad deed? Think about someone who is convinced that he is on the right path. That hes deeds are good and that only good things can come out of his actions. He is firm on his beliefs and he is certain that this is what he is supposed to do. And that it is good. But to someone else, the deed that he is about to do is not that good. Not any good. The person convinced about the goodness of his actions, acts, because he can, but that does not mean that he, or what he did, is any good.
For some reason I happened to read articles and Wikipedia texts about North Sentinel Island and the people living there. If you don't know what I'm talking about, read the Wikipedia link or glance it thru. Check out the part about a man called John Allen Chau. I will not start rambling about missionaries and what I think about those. I will only say this: What about all the diseases you took with you when you decided to go and die to the North Sentinel Island? Or the diseases you would have infected to the tribe if they would have not gotten rid of you? They just want to be alone, but you thought you knew better.
I know I should be respectful for those that have passed away, but in this case I think I will not shut up. I have to say: You selfish human! You ignorant idiot! With your actions, you could have wiped out the whole tribe from the face of the earth. Extinction. Extermination. Just because you wanted to spread the word. The word you think is the only, correct one.
So just because you could, does not mean you were any good.