A year ago, in winter 2018, I spent the Saturday mornings of eight consecutive weeks watching all the original Harry Potter movies in order, one movie per week. It was a nostalgic time. I looked forward to those Saturdays all week, perhaps because I disliked the life I had during the week so much. Nowadays, I don't miss the weekdays, but I do miss the Saturdays - so much, in fact, that I can hear Dumbledore's voice in my head from time to time. For example, in October, I talked about the war inside your mind and mentioned that he had said, in the fourth movie, that we must face the choice between what is right and what is easy.
Well, that quote was relevant in October. Now, I hear another Dumbledore quote in my head:
Happiness can be found, even in the darkest of times, if one only remembers to turn on the light.
This is from the third movie. Dumbledore makes a speech in the beginning-of-term feast and exmplains why Dementors are guarding the school. This is, of course, a metaphor. Dementors are creatures that suck all joy out of you, even so far that you don't have a soul anymore; therefore, Dementors can be seen as an allegory for depression.
In essence, Dumbledore is trying to tell you that if you're feeling depressed, you hold the key to getting better - it's up to you to click the switch and turn on the light, or choose to see the good things instead of the bad things, or do things that make you smile instead of sitting alone in the dark and hugging the Dementor in self pity.
Take care of yourself. Turn on the light. Choose to see the good. Ignore the bad, unless you can do something about it. And, as a personal addition, eat well, go outside for fresh air, keep a journal, write poetry, make your bed, read a good book.
Winter will be over soon.