You can't do that. You have to decide on one thing and concentrate. Make it your bitch. Practice it well for 20,000 hours. I can't stress this enough, you have to commit to one thing. If you can't do that, you'll continue to backpedal (and continue to feel unhappy, per your definition.)
You'll also need some sort of motivation. It might be a person you don't want to disappoint who is asking about your progress and who is there for you when you want to quit. It might be some internal drive for perfection... It doesn't matter what ''it'' is, but that thing has to exist and you have to be emotionally tied to it.
Of course, let me know if you can figure out how to find the one thing to focus on... I can't.