The second case involves not being able to stop whatever activity you're engaged in and go to bed, even though you recognize (perhaps briefly, before being drawn back into what you're doing) that you are tired and it would be a good idea. (This isn't quite the same as 'I'll do one more part, and then go to bed' in that it's less conscious and therefore harder to break out of - in many cases it takes a significant effort of will to stop your body from automatically taking the next step in what you're doing, even if you've actually decided not to take that next step.)

This sounds like me. Not just for going to bed, but for anything I need to do. Do you have links to descriptions or discussions of this experience? Have people found any way of dealing with it? I'm probably slightly on the autism spectrum.

ETA: I've also heard this described as ADD or OCD.