Great question. I love this kind of threads.
A lot of thoughts keep me up awake at night:
- (couple of months ago) dental anxiety.

I had a surgery last week, and I have two more to go, but it's not bothering me much anymore.
- how to earn money, since I'm a little broke and my only chance is my school allowance.
- thoughts about the future, about people I love, and what am I gonna do after college
- when I hear Katy Perry's Wide Awake. Effective.
- and some other stuff.