The key is to become self aware of your worth and see that you are an unique. When you realize that you won't take shit from others who place themselves above you, because you won't alowe it anylonger. Try goin to the gym. You know when you smile even if you are sad you become happy. It's because the body and the mind are connected. The same principe applyes here too. If your body is in good shape you will become more happy and confident.