Bit ago I had the same revelation regarding the short days as I did about cold weather/winter:
I only have so many days/week/months in the year. By choosing to stay inside because the weather is cold/dark, then I will end up missing out on a 1/3 of the year. I will go into hibernation even more so than I already do. All of this will mean I will lose that time, time I will never get back.
So I try to apply the same to the dark months: If I limit myself to doing only things when its light out, I will essentially get nothing done during the week, and spend all weekends/daylight time doing the things I have to do, versus what I want to do.

It doesn't make it "easier" or fix the problem; however, it serves as the fundamental motivation to get my butt moving.