I quit. Walked away cold turkey. I remember my last race at Downer's Grove in IL and then the 8 hour drive home when I realized I was done with bike racing like it was yesterday. Really heart-breaking at that time, really silly now. But 7 years later I came back. I was going to quit again at the end of last season but after five months off I realized I still enjoyed the idea of racing fast so I'm back to the grindstone (albeit at a fraction of time compared to the past). But I'll probably quit again in a couple of years. Or maybe not.
But quitting and trying new things can be pretty cool. In my 7 years of not riding I got fat(tish), traveled to 45 or so countries, did martial arts, ran and raced for 2 years (and got way skinny), went back to school, and did a lot of other things I didn't ever consider when focusing so much on riding. It was really great.
And when I came back my perspective on racing changed quite a bit for the positive.