I've done this since I was a little kid. I have vivid memories of waking up in the middle of the night and going downstairs to sit in my dad's chair and work on stringing beads or crocheting or sewing something, any kind of hand work I could get absorbed in. I'd nod off eventually, sometimes after hours of work. My mom was smart enough to realize that as long as I got up for school and didn't fall behind, there was no real reason to worry about me being up late. This is the only way I know to turn off the internal chatter.