From John Maxwell's book, Talent is not Enough:
The first and greatest obstacle to success for most people is their belief in themsevles. Once people figure out where their sweet spot is (the area where they are most gifted), what often hinders them isn't lack of talent. It's lack of trust in themselves, which is a self-imposed limitation. lack of belief can act as a ceiling on talent. However, when people believe in themselves, they unleash power in themselves and resources around them that almost immediately take them to a higher level. Your potential is a picture of what you can become. Belief helps you see the picture and reach for it.