If you're experiencing anger, sadness, or melancholy over the holidays, you're not alone. If you wish your stepdad would be civil to your partner, or that your daughter would have a baby, or that your partner cared more about holiday traditions, or that your friends lived closer, or that your house was larger, or that your aunt would drink less, or that your sister would stop yammering about her job, or any other imaginable wish you might have about how things would be better if only they were a little different from how they are now, you are not alone. There's a minimum of approximately 15,000 people all over the world experiencing exactly the angst you're experiencing, and for very similar reasons. It's too bad you can't instantly be in contact with them, because if you could, you'd feel validated. But as it is, you just feel sort of vaguely depressed and blase about various things. Which is fine. Just remember: you are decidedly not alone in this.
If you are like me, your assortment of discontents stem from a variety of specific reasons, but the same general reason: certain things are not as you wish or expect them to be. There is a picture in your head of what a really great Christmas or New Year's or whatever would look like, and your reality bears little resemblance to it.
You've got to get rid of that picture.
I'm serious. You've got to let go of how you would like things to be, and instead try to embrace how things are. Concentrate on the here and the now and the tangible. Think: this is excellent cranberry sauce, or: my mother has pretty hair, or: my dog is so incredibly soft. It doesn't even have to be positive. It can be neutral: my brother is talking about trains; I have a book in my hands and am reading it; my parents moved to this house when I was in fifth grade; my mother is stirring the gravy; my daughter's hair is purple.
Forget your ideal picture. The picture is fiction. The picture does not exist, and dwelling on the picture instead of the things and the people in front of you will not only make you unhappy, but more importantly, it will cause you to miss the good parts about what's in front of you. And even in an un-ideal reality, there are some good parts.
(Oh, for the love of God, if you're sad, stay away from Facebook, Instagram, etc. You may think that connecting with friends will cheer you up, but I guarantee that social media will make you feel shitty about yourself. People post distorted representations of reality, editing out the lousy stuff and presenting near-perfect or "charmingly chaotic" lives. We all do this. It is human nature to present ourselves in a socially appropriate or advantageous light, and this goes double for holidays. You don't need this right now.)
My mom says that the expectation that your life will look a certain way is like building a cage around yourself. I like that analogy, and I think it applies both to your own life ("I thought I'd own a house by now;" "My finances are a mess") and to your ideas about others ("I wish my sister was less critical;" "I wish my partner liked buying gifts"). I am convinced that a great deal of unhappiness could be avoided if we held our expectations a little less tightly.
So try, try, try your very best to get rid of your pictures and notions about what would be better. Try to accept people and things for who, and what, they are, even if their current state of being cuts sharply against yours. Letting go for the holidays will help keep you centered, will root you in who you are, and best of all, will make you more satisfied in the present moment to give you the strength to move on to the next one.