My story is similar to Salsa's. While I was never a racer nor did I ever compete in anything, I was getting to be a pretty good cyclist when i was dx with fibromyalgia. Although no one is really sure this is what I have, I have something and I have had to readjust my expectations. My goal is to keep riding (and x country skiing, snow shoeing, hiking, yoga) until I drop dead, but sometimes it is at a less intense level. But, I still work out 5-7 days a week.
I really recommend learning about mindfulness to help with your symptoms. The things that helped me were a 10 week mindfulness course, meditating, acupuncture, and counseling. All of those things helped me deal with different expectations when I had to.
PM me, if you want.