Here's a list of things that will definitely keep you up at night.
1. Think about your to-do list. Think about it hard.
2. Google cat pictures.
3. Wonder if you'll ever be as good at your job as that one coworker.
4. Call your mom. She'll just want to talk about the weather.
5. Reorganize your sock drawer.
6. Think about that time you accidentally superglued your shoes to the ceiling.