The longer you wait to call or e-mail somebody back, the harder it is to dial those numbers. The longer you wait to start a homework assignment, the harder it is to open your backpack. The longer you wait to do anything, the harder it is to do it.
I'm not sure if this has been proven experimentally, but I've seen it too much personally to discount it. I think that it has to do with a vague combination of cognitive dissonance and avoidance. You think to yourself, "but if I really wanted to do this, wouldn't I have done it at the first opportunity"? So you then deduce that you don't actually want to do it at all.
The main problem with this phenomenon is that it doesn't have a name, so I am naming it: obligation bankruptcy. This name is not totally original. I stole the structure from Chris Yeh, who a couple of years ago wrote about declaring "RSS bankruptcy." But now I am beginning to think that the name may be too long-winded, so I open up the problem to my readers. Any better ideas?
Coincidentally, I have been putting off this post for at least two weeks now. Thanks to Ben Casnocha for spurring a convo about it.