bigsombrero, I went through something similar recently.. and came out the other side.
I left a job end of May, went travelling for 3 weeks then came back. It was the flights and the unknowns that got to me. For me, I think it was adjusting to certain things that I used to deal with by drinking before. It had been an old habit for me to get a little bit smashed at airports, but I now know that I was always feeling really tired by the time I got to the other end. And I couldn't deal with travelling alone at airports.. go figure.
I also subconsciously don't like change, and can get depressed/anxious by it, I just didn't really realise how much until recently. This is despite most of these changes being of my own making, as in me choosing not to work, and now choosing to take another two months off to do a personal project. It took me a month (including travelling) to calm down. I've had to re-frame it in my head and realise that change and unknowns, even if scary for me still are also positive and exciting, and that now I'm making all these choices while sober. I'm no longer reacting while drunk or getting depressed due to alcohol/my behaviour. I'm actually really excited to be doing things I want to do now. I also read your travels on here, that has made me plan to go for longer trips next year.
I'm also using my time to get back into meditation and do more exercise, and see people I haven't seen for a bit, as well as go to AA (if that's not someone's thing I just find it useful to get in touch with other sober people or people who know me well to chat through any issues I'm having, which can be done online or other groups I find).
You'll be fine if you reach out to others to talk about it (like you're doing) and look at what's coming up as new opportunities. Which it is, good luck, will be nice to hear about it
And thanks for posting it, I don't feel so alone now.