I have always been shyish and unattractive..
But.... no, no, no, no, no. to the guys that hate Xmas and other things. There are all sorts of social get-togethers that it's easier to miss. For example, I used to dread parties when I was a teenager (ever had the feeling that at these things you won't quite be dressed right, and that everyone except yourself is going to score? ) - and in one sense I suppose we'd all have less stress if Xmas Day was spent sitting with ElReg and reading the other news.
Fine. Maybe pipe and slippers every night is the least stressful life - until one day you wake up and realise you've got no-one.
Family and friends (ex friends if you keep turning down invitations) are important. Get along to the Xmas thing; relax; ignore the uncle you don't like; don't think you've got to be faux-jolly; and be quite sure in yourself that *everyone* else is feeling awkward too. Stop worrying. Take a drink,. and enjoy the drink and avoid the crap buffet. And if you really feel that you've got to leave early, then do it. So what? What's the problem?
Life's never so scary as it seems. It's only a party, ffs, you don't need to be Ant-and-Dec cheery, and *someone* at that party is going to make a bigger tit of themselves than you could ever do. It's only a few hours out of your life (ffs again). Really, things aren't that important. Honestly.