Go to bed or keep working?
For me, the answer usually has to be "keep working." This is because I really cannot (or, at any rate, do not, ever) get up in the morning and get right to work. So if I go to bed, I may never recover the momentum that I feel right now, or at best I may recover it hours after getting up on Sunday. For the most part, I get stronger and find it easier to work more and more as the day goes on, at least when I'm vaguely able to structure my time that way.
I made the choice to continue working and I got some really excellent work done despite also feeling tired. Now it's 3:15 and I'm really quite tired and ready for bed, but I have big tasks completed. I also happened to stop at a "downhill" point, which is good. (By "downhill" I mean a point from which it is easy to continue. It's like riding on hills with your bike - if you need to stop, it's better to stop on a downward slant so that you can easily start up again.)
Basically when I feel "tempted" to work I have to make use of that temptation unless there are truly compelling reasons not to. As long as I get overall something like enough sleep, getting my work done is more important than sleeping at any particular time.