My doctor suggested surgery about 5 years ago, while I was still teaching, after PT didn't help much. I opted to wait and am glad I did. I understand that in many other countries they don't do surgery for bicep tears. I have been guilty of trying to carry too many heavy things, lugging multiple bags of soil, large branches, etc. when I garden, which I do extensively from spring through fall. I started being more careful----one bag at a time, using a yard cart, lopping the branches into smaller pieces to carry, and that backing off seems to have done the trick.
I also have heard what an extensive surgery/rehab the shoulder is---I am hopeful I can maintain, because it sounds awful. Obviously, when you reach the point, as you must have, where the pain and loss of mobility are too great, then you have to do it!
From the time I was a little girl, I wanted to be a teacher, so being able to spend 38+ years following my passion was a gift. Your friend is correct----lots of challenges in teaching are related to politics, excessive micromanagement by legislators whose only experience in education was that they were students at one time, unfunded mandates, etc. The challenges society is facing get transferred to our schools as well. Even then, it is a very rewarding way to spend one's life!
Sounds like you have been a bit of a trail blazer in your career---did you always have an aptitude for fixing things/exploring how things work? What a long, interesting career you have had! I am so happy for you that you will soon be able to get off those hard floors. Even when teaching, the floors are notorious for causing back and foot problems---being on your feet all day with thin industrial carpet laid over a concrete slab.