Well, the 'best code you can' isn't an absolute -- it depends opn the resources available
in reply to Re^2: what to do when you screw-up?
in thread what to do when you screw-up?
Exactly; the best code that you can write, assuming infinite resources, is possibly (even probably) not the best code for limited resources.
Oh, and there's another thing -- interruptibility -- if you're trying to keep your head down on a development job, but you *also* have to do support, double or triple your schedule.
Lost focus costs time; at one job, I found that I was terribly unproductive, despite my best efforts, when I had a co-worker who cleared his throat, loudly and repeatedly, every five minutes. It wasn't really his fault, but it killed my ability to concentrate. Eventually, he was let go... I don't know if that was why...