I'm in Australia, so it's summer here yet myself (and many others) are utterly miserable, and it's always worst this time of year. I think it's because there's this expectation that you have a good time - time with friends and family - "yay". For many of us, that is actually a bad time (many families suck), or maybe we have no one, or we have good families but feel isolated from them because they don't understand our mental/physical health/pain/unhappiness. It's also a time to reflect, and I've had a shit year, and I'm mad at myself because I promised myself last year it would be my last Christmas but here we are, doing it again. People remember those they've lost, and that's horrible. If you are financially stressed it's worse this time of year. If you have a job and have time off you have more time with your thoughts. If you have to work through the season, that sucks too because it's busy and people are rude and rushed in general. I feel like it's that thing of if something is meant to be a mandated good time, it will inevitably be awful for a huge group of people.