Not too long ago I bicycled to work every day. I always arrived cheerful and feeling awake.
Now I live 50 miles from work (job switch), telecommute four days a week, and on the fifth drive in and arrive cranky and irritable. I'd ride instead of drive (well, with the help of mass transit) if I could figure out a route that didn't scare me. Streets around my office in Santa Clara either go nowhere or are huge wide expressways with bicycle deathtraps (entrance and exit ramps) galore.
It's annoying that there are decent routes to get close to work but I haven't figured out a way though the last ~5-10 miles. My friends that have tried have all gotten hit by cars. (Car driver: I didn't see you. My friend: How could you not see me? I was wearing bright neon colors and seven lights!)