In theory, tapering (the last couple of weeks before an endurance event, when you cut back on long workouts) ought to be great. You've done the bulk of the work already (hundreds of miles of training runs vs. 26.2 race miles left to go), and (in theory, assuming you followed a reasonable training plan, and really did most of it) all that work means that you'll really be able to do it (with only a bearable amount of misery). Getting a good night's sleep counts as preparation. Hurray!
In practice, I hate it. I start feeling like it's been forever since I did a long run, how am I possibly going to run that far during the marathon? Every minor physical sensation is the sign of a massive disaster which is going to prevent me from doing the marathon (which, on the one hand, is good news because I'm sure I won't be able to run that far anyway, is also kind of too bad because then I'll have to tell people I'm not doing it, and there's no chance they'll understand the crisis that began when I noticed that I could feel my toes).
All this culminates in complete crankiness in the last hours before the race (before I ran my birthday marathon last year I was sure I had a speck of glass in my big toe, and yelled at Kevin about how we'd have to go to the emergency room in VT in the middle of the night before the race, so probably we should figure out where the Burlington hospital was now, just to be prepared...). Crankiness which magically evaporates (I think!) when I actually start to run.
The problem with the erg marathon, from this perspective, is that it's self-scheduled (at least the US version)--any time you want in the last 2 weeks of April. This allows me to combine tapering worries with a vague feeling of guilt because I could have done it already but haven't. Plus, there's the tantalizing possibility of just skipping the whole thing--without even the incentive of having paid a non-refundable registration fee.
So it turns out that it's a good thing I asked our coach (who also coaches the university crew) if I could use their team room tomorrow, and an even better thing that he checked with me today that I was still planning to use it... and that I said yes without thinking.
Apparently, I'll go a long way (42-thousand-something meters) to avoid embarrassment.