still can't sleep

Lately, the most anxious part of my day is the time between 3-7 AM when I am trying to put myself to bed. I am loathe to overuse the alcohol or the Tylenol PM because I don't want to be addicted to either of those things. I do have a fairly sedentary lifestyle, but even when I exercise or do something exhausting, I still hit an early-morning point of restlessness. Sometimes I'm a little happy about something, usually a little sad. Either way it takes a long time to knock myself out.
....I work in a place that never ever stops, so there's no feeling of closing up shop when I go home for the day. On my days off, I watch helplessly as all my normal acquaintences start to drift towards bed at civil hours, like midnight. I cannot conceive of being asleep at midnight. I don't think my body chemistry would allow it at this point.
....Most other parts of my life are pretty agreeable. I am active and occupied during the day, I have lots of things to look forward to, I'm creatively stimulated, I work enough to be financially secure, I like most of the food that I eat. It's just the sleep thing that vexes me.
....There are all these projects uncompleted, that I can work on at any hour of the day, but that will always be the case. I'll never reach a point of having finished Everything. So that anxiety in itself is not the problem.
....I know that my brother suffers from the same problem, so maybe it's some kind of psychological glitch. As introspective and over-contemplative as we are, it's hard to get the brain to calm down enough to enter sleep mode. There are just too many random thoughts to think and imagined scenarios to worry about.
....Then there's the obvious fact that I miss having someone to sleep next to. It seems that the grass is always greener there. There are other anxieties that come from having another body in bed, that made me appreciate sleeping on my own for a while. But that phase passed, and now I'm back to longing for the sedative effect of holding and being held.
....While the Winter Olympics were on, I didn't have this problem, because I could always tranquilize myself by watching curling, which is the dullest, most relaxing sport ever played. I'd put on the TV sleep timer and zzzzzzz. As of this writing I still have no idea what happens at the end of a curling match, or how, in fact, they end.