Losing my motivation

I know it's the time of year. Winter has gone on long enough and I always tend to get a bit sluggish about now. I just feel blah. I don't really want to do anything. I'm tired and if I could get away with staying in bed. I forced myself to go to Curves this morning but I tell you I didn't really work very hard. I need to get some sunshine and warmth back. Any tips to get over the winter humbugs?