Dark nights are very difficult I have SAD as well so especially so.It makes you inclined to just give in and throw in the towel.But with the SAD Keith made special effort,fire lit hot meal just extra looking after.
After he died the first winter was dreadful but I didn't help myself . didnt put the heat on or light the fire,didnt bother cooking just dragged myself home from work and went to bed.It has got better since because even though the cosy nights on the sofa with him can't happen I remember the effort he went to to look after me and it seemed like a betrayal to not do it myself..
So the next winter in advance I got a stove,not possible in every house I know but any radiant heater with a focal point helps,I made and froze pots of soup and stews ,stockpiled summer fruit and froze that too,so no effort to cook but nourishing comfort food to hand,and got a routine to make the time pass quicker.Even a boring routine can do that.I also make sure I get outside at lunchtimes if at all possible to make sure I got some daylight.It hasn't cured the SAD neither did he, but it has made it more bearable and that's something I have learned to do myself because I had too.
But at the same time as preparing ahead there is Autumn to come first,and it is the most beautiful time.So if you possibly can try and think about arranging a treat for Autumn,even if its just a walk in a forest,focus on that now and distract from thinking about winter now.