I agree with staying the course no matter what the market does, but from time to time it still makes sense to check your "course" and see if it's still the right one for you. I stayed the course after the 2008-09 meltdown, but after all that stress once I saw the market recovered a majority of its losses I redid all my numbers and realized that my investment goals could likely be achieved with a 55/45 or 60/40 allocation instead of the roughly 70/30 I had been using. (That would *not* have been the case if I panicked and sold a lot of stocks near the lows.) So a few months ago I scaled back my equity holdings to that level, and I'm prepared to again "stay the course" with the new course.
So in some sense this is letting bad market memories impact my investing decisions, but it wasn't a knee-jerk response based on gloom and fear. I didn't sell really low, I didn't panic, but when most of the paper losses were recovered I took a long look to see if (and how much) I could safely pare back my equity exposure and still have a good shot at reaching my target. Split-second emotional decisions based on fear and greed are wealth killers. But it is appropriate from time to time to ask yourself whether or not the AA you've selected still is, and will continue to be, the most appropriate given your own situation and risk tolerance.
I discovered what my risk tolerance was after 2008-09: just tolerant enough to not panic and sell out at the bottom, but not so high that I'm willing to relive that scenario with a 70/30 AA ever again.