Hey, in my opinion overthinking and procrastination go hand in hand. You keep thinking about something, and in that meantime avoid doing other more useful work, hence you just keep the work away. If you are mentally calm and have not done any physical activity, I think you should resist the urge to rest. Because that "rest" is actually just laziness. And as I said before, the best thing to do, is just start doing stuff. Don't want, don't think, just start.