OMG John I know how you feel. I opted out before retirement age as I just couldn’t do it any more.
What helped me in the latter stages of permanent full time work was to think of it as a rolling 6 month contract. A month before the 6 month point, Id ask myself whether I wanted to sign up for another 6 months and if I did, what did I want to get out of that time/ what would I do differently.
Psychologically it broke down the ‘stretch’ into more manageable chunks.
I also started to ease off a bit e.g. not working beyond 6 pm every day, not taking work home, trying not to get mad about things that I had no chance of influencing at work.
Anyway, sharing your pain and wishing you a happy 6 years …or maybe less !!!