@MynameisMaximus Yes, it is hard at times and easy to be envious and feel a bit left out when you see couples/families/groups of friends all sitting together and chatting, drinking, eating. Especially in the evenings as you say. But the way I look at it is that the alternative would just be being at home and I would much rather have a holiday solo than no holiday at all.
At least on holiday even though on my own it's a new and unfamiliar place to explore which is interesting and exciting to me and I can just enjoy that aspect of it and just being somewhere different.
Also as others have said, if you stay in an airbnb or similar at least you have your little nest to go back to in the evening, which is more homely than a soulless hotel room and also means you don't have to go out to eat at night if you don't want to.
Otherwise try to focus on the positives rather than dwell on the negatives - you can get up whenever you want, go to bed whenever you want, eat when and where you want, do whatever you want, no arguments or lengthy discussions about what partner/friends or children want to do.
But if you really hate the idea of holidaying solo, then perhaps look into activity group holidays, be it hiking, cooking, learning a language or whatever floats your boat.