When I was a kid, I would often sit on my bed and stare at the wall. My Dad would walk by my room and ask if everything was ok. I would always say "yeah", since I was literally just thinking.

It's a great feeling to just stare at a wall and think.

My first thought is usually, "If I could think about anything right now, what would it be?" And this frees my mind up to think about what I want to think about.