What a coincidence, I'm just coming out of such funk.
As to what I do , it's quite simple. I refuse to overthink it because once you do that, you get stuck in an endless circle. I tend to overwhelm myself with stuff to do and try to include as much people as possible, I also tend to focus on sports. It may seem counterintuitive but it works for me because sometimes you need to kick yourself in gear or you'll be in the slump for day/weeks.
Then again, if I'm in a funk because of tiredness I try to at least eat healthy, do some easy sports and hang around, just taking care of your body does wonders for your mind as well.