A few years back, I began noticing that while listening to car radio, some songs started sounding out of tune, like the singer was ending on the incorrect note, or the bass was playing in a different key. Not all the time, just periodically. Weird, but I attributed it to car audio anomalies.
What developed was that when performing onstage, certain notes in certain keys began hearing out of tune to me. Not every note in every key, but arbitrarily like the bass player was in a different key; e.g. the song being played was in A, but to me it sounded like it could be in F#, or D, or whatever? Very disconcerting! Ultimately I began playing in the positions of whatever was the correct key, and to the band and the audience it all sounded good and correct, but to me it sounded wrong. Not every song on the set list, and not in one particular key, but it made playing an anxiety experience instead of the one I used to look forward to.
Add that to the other things unpleasant about gigging at my age (78); long drives, late hours, heavy equipment, insignificant money, et al, it made playing music simply not fun and not worth it to me any more.
I consulted my next-door-neighbor physician who is an ENT (I've been wearing hearing aids for over 10 years). He told me that firstly, my problem is not in my ears but is neurological. It's in my brain, And because nobody is dying from it, there's little if any money for research into this situation; the vast majority of research bucks go to cancer, heart disease, and old age issues like Alzheimer's/ALS, etc.
He allowed as how there was a university hospital in Montreal that may be doing research in this abnormality, but 1. You're not a Canadian citizen, 2. Medicare wouldn't pay for it, 3. Montreal is an expensive city in which to live, and 4. no guarantee you could get in the program. And to what end? Do you have years to go in your career or are you near the end? In other words, just how far down this financial rabbit hole do you want to travel at your age?
He said, "Herb, you've had a great career for 57 years, you're recognized by many, and you're secure. By any measure you've had a successful life. You have all your faculties, and your extremities work. Maybe it's time to accept what your body is telling you, and get in your bass boat and go fishing."
So, that's what I do for my enjoyment, I fish here in TX and elsewhere, and my hobby is building fishing rods. I'm happy, although occasionally I get a little envious of other pickers who now play the gigs I used to play.
But I don't need or want a pity party - I've led a totally blessed life, and retirement could be HELL of a lot worse! 
(BTW, I have a few really nice steels for sale at reasonable prices, including a D10 Infinity, D10 PP, a lovely maple/rosewood Fessy, a pre-Clinesmith 10/10/8, and a T-8 Bigsby w/6 pedals. I'll post a list fairly soon.)
. I shouldn't be surprised that a close friend or two are playing the gigs I used to get called for, and in fact love my friends and they should play those shows. But I do remember the exquisite fun times when the gigs were good, the crowds, and so was the money et al.