Take your time! This has nothing to do with physical fitness. You see, some people are thin and short, but they are strong inside. Hitler is not a simple example. It's good that you can recognize your mistakes. If you can correct them, it won't take a day or two, but you must take your time. Try to chat with good people and make friends. Try to open your heart in crowded places (not asking you to run naked or anything) and read more books written by celebrities. It will give you great courage to feel like you. People! It is impossible without contradiction. In the face of interests, if it is small, it is okay to eat something small. You have to fight when you are older. Don't be afraid of these. Sometimes, it's not bad to be thick-skinned. Another thing is to open your mouth and talk.