I'm depressed and inactive because of weather (cold and no sunshine). What should I do to increase my energy and enthusiasm?

Seasonal depression. Get a dawn simulator, set to the same time every am, go to bed same time, push self to exercise or walk daily, reduce carbs in evening. If can't afford dawn simulator put bright light on timer to come on 15-30min prior to normal wake time. If still depressed, or if severe get evaluation for antidepressants, they help seasonal as well as other depressions. Also limit alcohol intake to 2 drinks.