i used to have a pretty high tolerance as well.. but like you, it seems those days are gone.
I have to question the reality of that.
My tolerance for pain is just as high as it has ever been, and it has been very high all my life. But some of the pain I get with fibro is pretty high also. I still call a pain a 6 or 7 when most people would say it was a 10. I think most people have not actually experienced 10 out of 10 pain unless, of course, they have had a rough childbirth. To me, a 10 means I cannot get up off the floor or couch, or talk or do anything but endure and possibly moan. If someone can walk into the doctor's office and calmly say they are having 10 out of 10 pain, they don't know what a 10 really is.
On some days, a tiny little bump that I would normally never notice is painful enough to make me gasp.
But for people with fibro I don't see that as being a lowered tolerance for pain. It is simply a higher level of pain, more frequently, than we have had before. And sometimes that continual dealing with pain will also wear down our resistance due to fatigue. But that is still not actually a lowered resistance to pain. Anyone will feel pain more if they are fatigued.
Most people, if suddenly given the degree of pain that you and I deal with frequently or even daily, would collapse, probably saying they have no idea how we go on, whereas we deal with it and simply carry on with our lives as best we can. Those of us who do that can still say they have a high tolerance of pain, in my opinion.