The biggest thing I've found is to just force yourself to do something sometimes. There has been many times I've not wanted to do something, go out to the bar, go to a concert or whatever, that I've just said to hell with it I'm going. Is it awesome everytime, no, but the ones that are were well worth the 30 minutes of mental grumbling.
So in short if you like hockey at least make time to go out and skate or play some backyard football with your buds. Played Rubgy and no rules Footbal in the winter many times with buds and had a blast that we still talk about. You just have to force yourself to make plans sometimes.
And yes I totally know what you mean with the seasonal depression, that's why I've adopted the practice of keeping busy, be it working out, being social. When you feel a bout coming on force yourself to go do something, sitting in the house only makes it worse man!