Argh - overdoing it - Arthritis
One of the reasons in the last decade or so that I have played less guitar than I would normally have wanted is due to the development of osteoarthritis in my left hand. In particular, the left thumb. This leads to there being some (ok, a LOT) of pain for repetitive movement.
And, if you can't grip the neck, you can't finger chords, and you struggle to play single note riffs cleanly.
Lots of Vitamin I (aka Advil or Ibuprofen) helps, but it isn't a cure. There is just a complete degradation of the cartilage in the base joint of my left thumb (and to lesser degrees in my knuckle joints) and the bone-on-bone contact is painful.
Alas, or ironically, playing more consistently has helped the pain, reducing it, and I have adapted to my - so far - minor motion limitations, and while big barre chords are agonizing, there are ways to work around it.
There must be something genetic to this malady in my case, as it seems that 10+ years on, the same side (the left) of my body's major joints are becoming arthritic. Ankle, big toe (ouchie), and left knee are all cascading the pain for me. Lovely!
But, as they say, it is as good as it gets, and as time goes on, it will continue to degrade. That said, while 7, 5, and even last year I was accepting of not being able to play guitar consistently, I will no longer accept that. I will work within my limitations, and take short breaks when I hit a wall, but continue to make the music that lives within me.
I can do this. I will do this, dag nabbit.