Took me almost a full year after retirement to learn how to sleep through the night without waking up.
I think that saveliberty is correct in that "having things on your mind" can really interfere with sleep.
With me "having things on my mind" means I won't fall asleep for hours but when I do I'll sleep hard even if it's only for a few hours. My internal alarm clock goes off between 7 and 8am no matter how much sleep I've had, what keeps me awake after that isn't worries, it's my allergies, sinuses clogged but starting to drain. My sinuses are also what will wake me in the middle of the night and keep me up for hours till the sinus rinse really take effect.
Sometime I hate getting older.........