Self-doubt is the companion that never leaves, that tries to insinuate its way into every moment of the writing process. Think of it as the infestation of termites trying to chew down your house of words. It is also, however—and this is why it is so insidious—related to a necessary caution that writers need: Is this the right word? Am I conveying what I intend to? Is there a better paragraph arrangement here? And so on. As with anything taken to extremes, caution can become disabling. The mind is a delicate instrument and responds badly to excesses of any kind.
Thomas C. Foster, The Seven Deadly Sins of Writing
Self-doubt vs. Necessary Caution
Christian Freelance Writers Network 