My initial impulse is to read this and swat it aside as an insult, with “Well, if I did it for attention from other people, I was an idiot (because I knew at the start that it didn't work that way)”. However, that objection fails to go through because, although I am not an “idiot” per se, I certainly do have some idiotic behaviors (or at least, some systematically irrational ones).
A more sophisticated objection: “Would you bother to write if there were no other humans (assuming all your basic needs were taken care of)? Well, uh, I dunno, I guess not. A-ha, then you must be doing it for attention from other people!”, also fails to go through, because it's really just semantics.
The truth is that there are a mixture of factors that prompted me to do NaNoWriMo. However, my intent in making this post was slightly different than you might have inferred. Specifically, I wasn't trying to cash in on the typical LJ “watch me whine, give me sympathy” thing, though there was little room to distinguish what I was doing from that in a presentation this spare. Note, however, the use of the mood “alone” (which, incidentally, to my surprise was not one of the default choices provided by LJ) rather than “lonely”. My goal, rather than to elicit sympathy, was simply to present (in fairly stark fashion) the fact that I feel a certain way. I recognize that there isn't enough evidence to make my claim here credible, though (not even 100% so to myself), so your criticism is well taken.
(Ug, now I feel like one of those post-modernist bullshitters who says “No, man, it really is art, you just have to understand the context”…)