Well. Once you notice yourself getting so good, your standard goes higher. With those higher standards, you'll start accepting nothing less than at or above that standard, for example: starting a drawing and not getting the post/anatomy/design right from the start because you usually can.
It makes it far too easy to slip into an art block without constant inspiration, and that can be hard. Though it happens to the best of us, and we all experience unique issues at all points in progress. But it's that factor of disappointment that can be tough to avoid.