I think that he is trying to tell his audience that you can do anything you’d like to. If you like something then go for it and try to do it as good as you can. He is saying that we are capable of doing it, we are smart enough.
To me what it means that you decide what you are going to do in you’re life and what you’re not going to do. For example you decide to listen to the teacher and do assignments then you will get a good grade. A bad grade is not anyone fault but yours you decided not to do that. When we are older we will decide if we will go to college, get a job, and buy a house, even little things we will decide like what to eat or to even go somewhere. So no one hold us back our mistakes are ours and when we do well that ours too.