It took me awhile, but I finally got it through my head that the pain was from muscles being torn down. If I ever wanted to progress I had to eat protein and continue the exercise. Then the muscles regrow, only stronger and maybe bigger.
Since I bought into that I realize that for most of us we either don't push ourselves hard enough on a consistent basis, or we binge exercise and suffer between binges. It takes some grit to explore the regimes of The Burn and The Pain. But, the long term results are well worth it.
Oh yes, this success in Spinning is just the latest chapter in a multi-year effort to improve athletic ability improve cardiac function and reduce fat percentage. It has had its' ups and downs (especially loco moco on the Big Island) but I'm getting there and hope to reach my goal in about two months.