Even worse is when motivational anhedonia develops into a full-blown existential crisis, where you fall into a Bartleby-esque† state of having no desire to do anything whatsoever. You know that you desire happiness in the abstract, but find yourself unsure how to achieve that desired state. You have no micro-desires, only this vague macro-desire, which can lead to an almost intolerable malaise. At that point you've basically crossed the line from "procrastination" to "mild clinical depression."

I'm not really sure why I typed all this out since I don't have much of a conclusion, but I'm going to leave it here in case someone finds this relevant to their own situation.

† http://en.wikipedia.org/wiki/Bartleby,_the_Scrivener