The issue is meeting waiting somewhere for the sole purpose of someone who never shows. THAT is what causes me anxiety it’s not just being on my own
I feel the same. If I go to a coffee shop by myself I know I will be alone and plan accordingly. I go when I like, at a time to suit me, and if I leave later than planned then it affects nobody but myself. I
find a table in the corner, bring a book or a podcast, and just allow myself to relax in my own company. When I am done or if I start to feel anxious/uncomfortable - eg if it is busy and there are no empty tables and people are clearly wanting my table while I dawdle over the last couple of mouthfuls of coffee - I can get up when I like and continue with my day.
When I am waiting for someone, it is not relaxing at all. I try to ensure I have a table visible from/to the door so I can see my friend arriving, I then spend the entire time watching the door for their arrival or my phone for their latest message. I also rarely enjoy my drink as I am usually trying to make it last as long as possible in the hopes my friend will either turn up when I still have most of a drink so I dont have to buy another, or at least before I finish so that I dont have to sit too long without a drink especially if it is busy and people are waiting for tables.
I also hate having to get up from a table to re-order when im alone as I hate leaving my things unattended but I dont want to have to cart my stuff to the counter and risk my table being taken while I'm paying.
Additionally, I cant just leave when I like but after so long alone I start to think of all the other things I could have done in this time and start to resent the fact I was on time. "I've been sat here 30 mins, if I'd gone straight home when she said she was going to be late, I could have put on that washing, picked up that letter I needed to take to the post office (but forgot to pick up as I was busy trying to get out of t door on time), stopped to check if XYZ I've been waiting for is in stock at ABC shop round the corner and still been back here by now, but it's too late to leave now"