Where would you go for first solo trip?

I went on holiday alone for the first time last year with Just You, who cater for single people. There are many advantages to this - no irritating single supplements, your own room at all times - and the knowledge that everyone else is on their own too. I went to China, which is somewhere I had always dreamed of visiting, but they operate a full programme, with shorter trips and some in the UK, which would be good to try out and see if it's your thing.
There were about 40 people in my group, with ages ranging from mid 30s to 80s, although the majority were late 50s and 60s. For some it was their first trip alone, but others were old hands.

Just You has an online community where you can chat with others who have booked on your trip before you go, and a moderator who will answer any questions you may have.

There seemed to be quite a few retired teachers on my trip, and I made some great friends. We have all kept in touch and in fact are meeting up in London next month for a reunion.

The prospect of going on holiday alone for the first time is very daunting, but you'd be surprised at how many people are in the same boat. You're not as alone as you think! Go for it!

There are definitely travel firms who specialise in people travelling alone - whether single or by choice because their partner doesn't share their taste in holidays. I have had no personal experience, but might also suggest an activity holiday - walking/painting/historical interest/architecture etc if that might appeal to you. I am sure you will find congenial company and hope it works for you.