I would recommend looking into being able to recognise ‘thought viruses’

A book that really helped me was ‘Stop overthinking’ by Nick Trenton. I still have those thoughts, Anxiety isn’t the easiest thing to get rid of.

Find what it is that you enjoy, build habits (tiny habits / atomic habits are great references) and you might find that just moving a tiny bit in the direction that makes you happy might compound over time.

Success isn’t always about careers or large paydays. Your health, relationships, hobbies, identity and sanity play a big part of that as well.

I have friends who moved to other countries and restarted their lives at the age of 35/40, and I met people in their 70s who done the same.

Good luck!