Strength is powerful, both mentally and physically, and both come from doing things you never thought you could do. One of the most satisfying things in life is surprising yourself. I've pushed myself out of every comfort zone I've known at some point or another, and it's made me a better and stronger person in every way. Never tell yourself you can't do something before you try! You are all incredible, and capable of more than you know. Start trying. The worst that can happen is that you'll learn a lesson, and a little bit more about yourself :)