I kinda had that before, I'd say from the moment I started my adult life to 5-6 years ago.
A kind of dread that whatever happens, I'll miss out on something.
When I was a kid, spring meant that the long summer break was getting closer and it was just pure joy for me.
As an adult, in a job and in a relationship, it was different. Spring / Summer meant my birthday, so getting older, and that feeling of missing out crept in. I felt like I was missing out excitement, career opportunities, and just novelty really.
And to be honest I think my way to bring excitement and novelty in my life was to party hard. I needed excitement on a daily basis because my day to day life was feeling quite bland.
My real issue, I think, was that I had no long term goal, no perspective at all, I was just living day to day with that feeling of missing out, I had my eyes on a future without perspective and felt like it was always slipping between my fingers.
It all changed when I turned 35, a chain of events led me to make radical changes in my life, and eventually, I moved abroad, developed new skills, which led me to have some tangible goals, and now I feel aligned with myself if it makes sense.
But it's only once I gain that alignement that I realised how mis-aligned I was before.
(sorry very long post to say "Yeah I think I get what you mean"!)