I may have written about this here before, but the end of the semester has always been a productive time for me to write, especially when my teaching (as it sometimes does) converges so perfectly with the stuff I'm working on. But even more than that, the drive-to-write is a leftover habit from grad school in which the end-of-semester time presses down on everything, and deadline-panic gives way to focus.
This vestigial habit reminds me of another habit that didn't die with the conditions that produced it--the one in which I bit my nails throughout basketball season, beginning in mid-October and stretching through early April. These were high-stress, nervewracking times, etc. But weirdly after my playing days were over, I noticed that I did the same thing in graduate school: starting in mid-October, for no apparent reason, I began biting my nails. I eventually retrained myself and don't do that anymore.
By contrast, though, the vestigial habit of intense end-of-semester writing has its advantages, so perhaps I'll hang onto it.