"Cultivate thy own powers, to study and become wiser, to become more skillful, to so act as to respect thyself. Thereby shalt thou acquire confidence in thyself to achieve thy carefully considered desires." ~ The Richest Man in Babylon
Your source of self-confidence is knowledge. Your ability to acquire knowledge is limitless.
"...it is not insofar as he is man that he will live [a life of contemplation], but in so far as something divine is present in him. If intellect is divine, then, in comparison with man, the life according to it is divine in comparison with human life. But we must not follow those who advise us, being men, to think of human things, and, being mortal, of mortal things, but must, so far as we can, make ourselves immortal, and strain every nerve to live in accordance with the best thing in us; for even if it be small in bulk, much more does it in power and worth surpass everything." ~ Aristotle Source
What I lack in knowledge I make up for in enthusiasm.