I've done a decent amount of work for this point in the day. If everything had gone swimmingly I would take a break and do some personal emails, write up, check in, and work out what little jobs could be done in another couple of hours.
But because every bug revealed another one, in terms of making the picture prettier, I feel like I haven't achieved much and must go on. This feeling, of "must do this" is what prevents me from doing other stuff which must be done, because I'm sure I'll get what I'm doing finished in another half an hour... but don't. It's the same feeling that can persist for weeks on an ongoing project.
There's much definite progress -- the image is encoded correctly in the vast majority of 4x4 blocks, but some are 0x40 off. It's clear where I have to go next. But I have a nagging feeling that the fixes I've done haven't been quite complete. And realistically I'm too tired for much debugging, a short break would help.
And because I'm strong, I will write up what has to be done next and leave it for a little bit, and then come back with inspiration.