A late reply, but thanks to all who have contributed to this thread!
@Janette Haha, I've noticed that too, how doodles will often turn out so much better. Yesterday, I actually managed to do some decent sketches for the book project I'm working on, just because I was talking to a friend on the phone while drawing. Strange how that works. Maybe I just need to find more ways to distract those parts of the brain while I'm drawing. Thanks for the encouragement!
@Alzamon I've realized that I've automatically become less and less active on social media this past year, probably because I just don't have the energy to keep up with the high pressure-low reward ratio. Even though I'm stuck more than usual these days, I think it would have been even worse if I hadn't cut down on that pressure. When it comes to ideas, I usually have the problem that I get frustrated that I have way more ideas than I feel I can express. In some ways it's better than the other way around, but still frustrating.
Switching activities, like you say, is the only thing that has consistently worked for me. Since I started this thread, I switched to rendering a lot of drawings that I had done the line art for. It worked quite good to relieve the pressure, even though I'm still a bit worried about those drawings I still have a deadline for but haven't even started on yet. Thanks for the reply!