Mostly running and trail running with a little bit of road cycling now, rather than vice versa in the summer. Other than that I tend not to notice all that much, I prefer lighter nights but what you gonna do.
I notice I really have to try hard to manage my thoughts and pushing myself to exercise. Didn't ride my MTB all year (bloody golf, getting rid of the membership at renewal - I'm the wrong side of 40 to be dropping proper exercise) but have been out in the mud a couple of times since Autumn hit.
I mug myself off believing the garmin's monthly badges/challenges mean something but they really keep my momentum going into winter if that helps anyone. (picture those generals standing next to Kim Jong Un with all their medals - that's me that is!)