Strangely enough, doubt need not impede action. If you really become friends with your doubt, you can go ahead and take risks, knowing you will be questioning yourself at every turn, no matter what. It is part of living, a healthy evolutionary adaptation, I would imagine. The mistake is in trying to tune out your doubts. Accept them as a necessary (or at least unavoidable) soundtrack.
Phillip Lopate, The Essay, an Exercise in Doubt