Out of sheer curiosity, do you happen to know Charles S. from Michigan? He asked a question about how to get into NBA.
I cannot agree more with what Marcelo pointed out: self- determination, getting inspired, etc. One thing to add is get yourself into a college with prestigious basketball program and surrounded with like-minded people. As long as you don't give up, your fellow players will "force" you to stay motivated.
Choose goals that interest you. You’re much more likely to stay motivated if you’re working towards something that you genuinely want to do or achieve, rather than what other people want for you.
Find things that interest you within goals that don’t. Sometimes other people set goals or tasks for us that we don’t find interesting or want to do. So, try and find something within that task that does motivate you. For example: ‘I find maths challenging, but it’s going to help me become a builder, which I want more than anything.’
Make your goal public. If you tell someone – or write down – your goal, you’ve essentially made a promise to keep your word.
Plot your progress. When you’re working towards something, it can be really motivating if you can see evidence that you’re making progress. Draw or create a visual representation of how you’re coming closer to achieving the goal you’ve set yourself.
Break up your goal. Start with easier tasks and work your way up to bigger challenges. Breaking up a task in your mind into achievable chunks helps build confidence.
Use rewards. Promise yourself some sort of reward each time you complete a step/task.
Don’t do it alone. Join a class, or find a teacher or someone you can share the experience with. Other people’s encouragement to keep going can be a big boost to your motivation, particularly when you’re doing it tough.
More at https://au.reachout.com/articles/tips-for-getting-and-staying-motivated