When I used to live 4 miles from work and didn't need to lug loads of heavy stuff around, I used to ride to work on average two or three days a week. If the weather was nice and I was in the mood, I rode. If it was really windy, raining, or snowing (rare in London), or I just felt a bit rough, I used to drive or get the bus. There's no prizes for being a masochist and riding in horrible conditions or when you are feeling a bit below par. Cycling must never feel like a chore to be endured, otherwise the motivation for doing it goes out of the window and the temptation is to jack it in.
I’m with you, I’m definitely a fair weather commuter. Finishing work on a Friday and cycling home in just trousers and a shirt in the sunshine is a very pleasant experience.