What do you want to do sadhana for? The aim should not be the satisfaction of egoism: "I want to be a great yogi; I shall have so much power and with that power I shall establish myself in the world." All such thoughts must be thrown far away.
They will always tell you that you can't do what you want to do, but you can do what you want to do. You just have to believe in yourself. The system is to bring you down, but you can rise up.
How I feel is that if I wanted anything I'd take it. That's what I've always thought all my life. But it happens that I want you, and so I just haven't room for any other desires.