I'd also recommend mixing it up with a longer ride on the weekend, but you may also want to consider picking a couple of other routes to and from work. They may take a little longer, but it's good for you to break up the routine a bit to prevent it from getting too stale.
The #1 thing that makes my commute better is leaving early, taking it easy, and arriving early. If you're constantly rushing to get to work, it stresses your body and your mind before you've even started the day. Make sure you're out the door with lots of time to spare, use those gears and don't be afraid to just coast along. You'll arrive in a much better mindset, with your heart and head ready.