Any ride is a good ride, so don't beat yourself up. Listen to your body; if you feel tired, take it easy, if you have energy to spare, then ride harder or longer. But whatever you do, don't ride to exhaustion where you can't recover or lose interest.
I'm learning quickly, that winter riding is tough, it's not easy and with all the extra layers of clothing plus the extreme conditions, it takes more effort to ride the same 20 miles then it did in warmer weather.
I'm not at the point I feel or want to ride everyday in cold weather. So if you're committed to riding through the winter, I applaud you, for your dedication and determination, that's not easy.