I don't know how to attain peace of mind

There are so many conflict idea in my mind, they always quarrelling with others. and they never get thereach a conclusion. When I want to concentrate my mind to do something,such as to focus on my work. they always push me back from doing good. Oh! God! There is a cabinet in my head! I don't know how to get rid of it. It's easy to make some simple matter became complex, like my mind, but It's impossible to reverse that process. I doubt if I have read too much book. that made me confused. or something else I don't know. I really want to go back to simple, back to foolish, I need to gain peaceful mind.