Thanks for the reminder, wk17. To get unstuck: *pomodore*. Set a timer for 30 to 45 minutes, under which you are only allowed to concentrate on a single thing. No email, no looking up why your editor doesn't find declarations, no tuning of the red color of your terminal that is to bright, no compulsively opening devRant.
Time's up, do whatever for 5 to 10 minutes, and repeat.