Hello and welcome. Your story resonates with me. I, too, started late ... picked up the classical guitar at 45 setting a goal that I should be playing grade 5 repertoire by age 50 and here I am doing just that.
* Do not wrestle with music that is beyond your scope. Keep a couple of these to work on as your technique improves but there is plenty of beautiful music for beginners. I used the Royal Conservatory of Music series, started with the P level and then marched through grades 1 to 5 , one per year.
* Find a teacher. I did the first few years alone ... with a teacher things got much better. I had someone to listen and to challenge me and to help me improve.
* Compare your music to your music. There will always be people who play better (more skillful, more time, just more talent). It is tough as a adult to see someone who is 1/2 (1/10, in your case
) your age playing much much better. Keep a journal. Set goals ... and watch yourself improve.
* Do not push. No pain. That is tougher, too, I find as I get older. Work on good posture and technique.
PS: There is thread on here where someone asked if you could go back in time and talk to a classical guitarist who would it be ... someone very clever said that that they would go back in time and talk to their 20 year old self to get them to start playing guitar.
Enjoy the music.