Hi OP,
The most important part is to go, go, go! And the second most important thing is 'Don't look down!' just go for it, you'll be FINE!
Might you fancy going somewhere familiar and catching up on sights you haven't seen? (e.g. Paris has loads of museums and cafés in different areas; I went to some places with a friend from uni that I hadn't visited with my DH)
Don't be afraid to sign up for a package for your first time. There are 'singles' groups going all the time. At a minimum, you can hate them. :)
Or do you have a hobby/activity? Other friends of mine sign up for a cooking course or a painting course or a history tour/walk through a Belgian/Nederlands city. This gives a focus to the day, an activity they like and a chance to meet other likeminded travellers. Other friends have found a language course and gone to a lesson each morning in the local tongue and then practised all day.
From UK the western world is your oyster via short flights: do you want a winter break, relishing the dark, maybe to the northern lights (teen DC and I are doing this in Feb half-term), or do you want a warmer weekend so south to Spain (we had a great week in Barcelona over Easter with DH pre-covid), Portual or France?
Once you've had a great holiday, you'll be back in the saddle.