If you haven't read Paul Arden's It's not how good you are, its how good you want to be. Then you must. I found the first book far more motivating than the sequel. I gave away a half-a-dozen as gifts, well every book I bought myself , people wanted to borrow. I couldn't part with them, so signed them away as gifts.
They are both worth your time, a quick read and a reminder to lead a life less ordinary and taking risks. Its a pep talk, as well as an instrument to kick your butt -- all in good intention to help you overcome your shyness and be an assertive creative.
Quotes from the books...
"You don't have to be creative to be creative"
"If you want to be interesting be interested"
"Don't seek praise seek criticism"
"Knowledge makes us play safe. The secret is to stay childish."
"Don't go to university, go to work."