[zgoat]

I think this feeling is often eliminated by hindsight and change of circumstance. I've had the same sensation at a few points in my life until I broadened my fields of study, took on new roles, went broke etc.

In my own experience it's in the category of "You don't know what you don't know". If you are highly focussed on a narrow field of study or experience, yes, you definitely feel like you have "peaked" with respect to mastery. However, once you get exposed to "You now know what you don't know", a lot of things suddenly change.