I think it's normal to lose motivation at this time of year, if you've been working really hard on the bike. It's your body's way of saying "enough!" I've dealt with this by doing a lot of different activities, to replace the cycling. If you have snow, snow shoeing or x country skiing seem to give me the same feeling/intensity as cycling. Hiking might not be as aerobic, but it sure works muscles I don't usually use. I also started using a trainer at home, along with a strengthening/yoga program. I find I really look forward to that, when the pressure is off because doing it at home means not having to go to the gym. I still go to a spin class once in awhile or run on the treadmill at the gym and outside. Another thing is take out a mountain bike! I generally suck at mtb, but even if you're going slow, it demands a type of concentration and fitness that you don't get on the road bike. And, it helps your skills on the road. You can get out on a mtb in weather that is a lot colder than my comfortable limit for cycling on the road. You will be fresher when the season starts if you do some cross training now and build some cycling specific skills on the trainer or at the gym. And have fun!