OMG, I've been thinking I have a mild bipolar disorder- and now I read your post and it sounds just like myself. I occasionally still doso- the other day I went for a walk starting at 3am and came back home around 8am. I used to walk at night all the time when I was unemployed in 2009. I know it's not safe and have cut back quite a bit, When I was in college I used to do it a lot more too. I love the quiet of the night, emplty streets, its all so beautiful and peaceful.