I used to fall asleep as soon as my head hit the pillow. Until I hurt my back. With chronic pain, it's highly unusual for me to sleep more than 3 or 4 hours in a row. Most of the time, I wake up within an hour of going to sleep, but I can go back to sleep. After doing that a few more times, I'll get up and read in the living room in my recliner, or I cross stitch and watch an old movie. It's very hard to be at the top of your game when your sleep is so interrupted.
I know that I've experienced the first night syndrome and the reverse first night syndrome. Two weeks ago, I went to visit my aunt and was there two nights. Then Jay and I went to Georgia to pick up his mom, and I had one night there. Both times I had a hard time sleeping while there, and even when I got home.