Fully agree Earthshine.
Last couple of years I've decided to go running (well, a slow jog!) every morning, whatever the weather. Mostly on-road during the dark months, but various farm roads and cycle trails can be done in the dark and wet too. I don't use a torch, lots of light pollution/ pre-dawn light when away from streetlights when you get used to it. Just getting outside, whatever the weather, has made a big difference for me. I'm glad of the light mornings now and slightly drier trails as I can stick off-road more. However, part of me misses the dark, it gives a comforting focus. Lots of weather changes, moonlight, owls, birds singing under streetlights etc keep the "dark" runs interesting. Getting cold and drenched gives a satisifaction afterwards!