I have a task list; each task has been allocated either 0.5 days, 1 day, 2 days, or 3 days. Actually, I think I subdivided everything over 1 day.
A lot of the 0.5 day tasks were really tiny, but knowing from experience there's no such thing as a 1-hour task, I assigned them all a minimum of 0.5 days. One issue there is that once I get a task done, I tend to slack for a while, or even just go home, even if it took less time than allocated.
The timing was looking a little tight for getting everything I need done in time for the submission time (I don't have to have the game complete--I'll be submitting it with placeholder art--but I need to get the gameplay solid, and I'd like to have some of the flashy graphics done).
However, today I got done a one-day task and six half-day tasks. Yay me.