I occasionally go through periods where I have trouble sleeping. They re-occur occasionally ever few months to a year. Generally they seem to be triggered by work related stress, or sometimes just the stresses of life. They never happen on weekends unless I have something important to do like a long drive or travel. I don't sleep as much as you normally either (usually about 6 a night, 7 on a good night).
As others have noted, what works best for me is some very hard exercise after work, enough to wear me out completely. Fishing works great for me as it really clears the mind for me personally. Also, sex before bed helps but that isn't always an option if your single. I find that alcohol will help me get to sleep, but I end up not getting as much rest out of my sleep/waking up alot during the night, unless I drink a ton... and to drink that much I'd be a mess for work in the morning.