Ever heard the song "Don't Stop Believin''' by Journey? It's the kind of song we ought to hear whenever we doubt ourselves, which, for some of us, happens all too often. But the fact of the matter is that we have no choice but to believe in ourselves -- because no one else is going to do it for us. A lack of self-confidence impairs our ability to land dates, get jobs, build relationships, and -- most important -- enjoy life. Doubting ourselves can lead to low self-esteem, which can in turn snowball into depression and other more serious health outcomes. Once it becomes apparent that many of the excuses you concoct for not succeeding are in your head, you come to realize that you've been holding yourself back for no reason at all. Maybe your parents or peers told you that you couldn't achieve something and brainwashed you against yourself. But how would they know what you're capable of if they're not you? A person can achieve anyt...