Poor sleeping habits
Lately I find I wake up at least twice during the night. What this means is that I end up getting sleep, but only in around 2-3 hour blocks. As a result I'm not sure just how much quality sleep I'm getting these days.
The worst part is when I wake up at like 5am during the week, because then I'm really screwed. Going back to sleep ensures that I won't wake up till 8, and staying up means that I'm sluggish at work all day.