I was on a night ride to Brighton, five years ago. I felt pretty dreadful just getting to the start, and nearly bottled out at Clapham Common. Somewhere in Mitcham (I think), there was a small railway bridge ahead and I thought "There's no way I can get over that!", and turned for home. Three weeks later I was under the knife having a double coronary bypass, a completely undiagnosed condition until four days before the operation. I guess my body had spoken on the way to Brighton. Anyway, I managed Ditchling Beacon for the first time in my life six months later, and I've wheezed up it a few times since. Just ride your bike and enjoy it.