HN user
I lived on around 13k after taxes all through college, it isn't that hard. I still spent money on going out to eat, computers, etc.
Assuming you are single (otherwise, this whole exercise changes), then they biggest factor is room mates. 2 people sharing a 2 bedroom apartment (and utilities/food/etc) can easily live comfortably on the $15k-$17k after tax income each.
You can easily get MUCH cheaper by having 2-3 room mates.
You need to internalize a desire to use the finished product. In otherwords, you have to want the finished product.
This is probably a horrible misquote, but I remember a long time ago John Caramack saying that what drove him to fix all those little stupid bugs at the end of a product was the desire to play the finished game.
Others who just wanted to ship it were having a tough time sticking with it since they just liked developing cool tech and wanted to move on to the exploratory phase of the next project.
Now, if it's a clients website you have absolutely no interest in and can't figure out a way to have an interest in (coding for it's own sake), you've got bigger problems :)