This winter has been unusually warm for me, apparently it's part climate change and part normal stuff.
The darkness still poses a challenge, and I struggle with going outside, so I've tried to make my room as nice as possible, because that's where I spend most of my time. So if you're spending a lot of time at home, try to spruce the space up a little. Make your bed comfier, clean up a little, maybe decorate a bit if possible.
Find something nice to do inside, like a show to watch or a book to read, a game, or a craft. Or if you're more outdoorsy, I guess you could find a winter activity (sledding or skiing when there's enough snow, fishing if that's your thing and you have a place to fish) or maybe just learn to see beaty in nature even when it's grey and wet and cold.
Ihave begun to accept that I simply will never be as 'productive' in winter as I am in summer. One option can be sleeping more, I feel that that's helped me make it mentally.