Hi Shady,
I definitely don't grin. So I can't grin and bear it. I guess I bear it.
I hate being such a mush, but there are times when I end up sobbing (as quietly as possible). Like you, I've had that kind of excruciating back pain happen at work. I noticed sometimes that if I'm able to work out a some kind of BM (big or small), I'll get a small easing of the pain.
I don't usually get back pain when I'm crapping a storm. It's like food of some kind migrates to a particular spot and goes real slow, and the back pain kicks in and stays. Once I had it at my GI's office. When he put pressure on my bowel, I could feel it in my back - that's when I realized it wasn't actually "back pain" per se, but "flank pain".
What works best for me is to lay down as soon as I get home, probably an hour, then I can walk a little better again. Then I stay to liquids. I use this protein mix that gives me balanced nutrition and I don't usually eat for the rest of the day - not usually hungry anyhow.
That's probably not much help, but there's not much that works for me either.