Quite honestly, I don't think it's unique to writers. Why else would we talk of "one hit wonders," if there weren't at least some bands and artists who freeze up at having to follow that initial success with a second song, a second album? What about the artist whose work is acclaimed, and now has to go back to the studio and try to paint another work that lives up to the expectations created by that initial success.
And I really doubt it's confined to the creative arts. How about the inventor or the company who produces a wildly successful product. Now you've got to produce something else that capitalizes on that initial success.