I have psychomotor retardation (thanks for putting a name to one of my biggest struggles!) due to major depression but exercise really does help more than anything else. It's definitely hard to exercise, but often it's not that I can't do anything at all, it's that I use up all my willpower doing one thing in a day. But if I make that one thing exercise, then for the rest of the day it's like my psychomotor retardation goes away completely and then other tasks are manageable. I actually brush my teeth, do the laundry that's been piling up, make a healthy dinner and clean up the kitchen after, etc.