I have a bit of insomia on occasion too. What helped me is yoga at about 8pm, and no caffeine after lunch. Still, when it's really bad, ie. I wake up at 2 am and can't fall back asleep, and now it's 3:30... I take 2 Benadryl(Tylenol PM minus Tylenol) and within an hour, off to lala land. The big problem with insomnia is that if you don't really have any other issues, doctors don't believe you.
Another issue with sleep I have is that sleep VERY lightly (if I'm sick, I don't go into REM without meds.), as in my cat is downstairs playing with her "crinkle ball" and it wakes me up. No jingles, just rustling mylar half a house away. Sometimes, this can be bad, in that case, a Benadryl keeps me deep enough under to stay there.
And insomnia isn't always mental illness. I talked to a psychologist a few years ago, she didn't think much of anything was wrong with me. Sometimes, insomia is genetic or medical, though I don't know how much they add to it.
My mom's an insomniac... bad.
And she's mentally healthy, if anyone really is. Both my grandmothers are the same way.
So, it's not alway psychological, sometimes it really is just how it is.
Anyways, yoga was really helpful in calming my mind before bed. A steaming hot bath and a stupid trashy romance novel seem to help a bit too.
Good luck!!