I come from a long line of hermits, hyper energy, and night owls. Staying up is no problem. Coffee actually negatively affects me. Half a cup, and i'll be fatigued for at least a couple of hours. I switched to alcohol for doing homework (the damn drink gives me unnatural persistence even when i want to take a break or quit, great for doing 2 weeks worth of homework in a night).
I'm in a similar slump right now, but a little different. For me the difficulty in performing tasks in my current jobless situation and my energy level is that i only want to do fun things. I have given projects for myself to do in the mean time every day (tasks that need to get done, and some that i keep putting on the back burner that i really want to do...that would take a long time). And it's been good. I've also been working on getting out of bed earlier. After all, i love to play dance dance revolution all day, ride my bike for miles on end as fast as i can, stay up late, and wake up late. That's what pulls me from turning a via nano mini itx desktop into a router, making a consistent website that matters, winterizing the above ground water line, and working on my currently broken bike (riding them is more fun than fixing).
I have a few things to say. Collect your thoughts and make a list of things you need to do and things you really want to do. And do them. Especially when nothing else is happening and you don't feel up to doing whatever. Even doing small things like listening to music that lifts your spirit should have an affect. Techno, dance, jpop does that for me. I recommend that because if you feel better you should feel more up to tasks. Most people don't like to do things if they feel ****ty emotionally or physically.