The next time you think "I am just not good enough" instead think "I am just not good enough YET!" (paraphrased from Heidi Grant Halvorson's blog here).
Innate talent has been shown to be a very small component of most expertise. I have blogged about this before but Heidi's blog post made me think of another important component. The book Talent is Overrated has some great advice on the how and the why. But Heidi gives a short and sweet motivational message on the visceral motivation. You have to believe in yourself. To loosely paraphrase Yogi Berra, expertise is 99% practice, but also 50% desire.