The Christmas that you dread isn't here now. The relationships that ended aren't here now. Your friend who met a new partner isn't here right now.
Recognise that these, and all other things that are causing you grief, are entirely your own creations. They exist, right now, only in your head, and as a result of that, you are in charge of them. You are 100% responsible. You are the only person who can do anything about them, or your response to them.
If you just sit there, right now, and work out what is actually wrong, right now, it's highly likely that nothing is actually wrong. You are warm, dry, fed, safe. If you want to go to an art gallery or go on a date or walk outdoors or book yourself in for parachuting or guitar lessons, you can. Nothing is different for you than it is for anybody else. Some of us are single, some not. Some of us have lots of friends, some don't. Some of us are busy, some aren't. There's nothing special or unusual about your situation. It's completely normal.
You say you have nobody, as if 'somebody' could come and take all this sadness away. But you have you. Why aren't you doing that for yourself? Why would you think anybody else can do it for you if you can't do it?
What would you like your life to look like? Is it literally the same as now, but with somebody holding your hand? Or would it be a different shape, with fun activities and pastimes, lots to do and interest you? If it's the former, hold your own hand first; look after yourself. Do nice things, to soothe yourself. If it's the latter, just do the activities you'd like to be doing. You might meet the partner there, and you'll be much happier, and so in a better position to have a healthy relationship.