I've made the call a few times due to my heart condition bugging me. Once it was the combination of that and cool weather - I couldn't work hard enough to warm up. I've had one debilitating mechanical but I was close enough to home to walk it back.
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Genesis 49:16-17
"Well, well!" said Holmes, impatiently. "A good cyclist does not need a high road. The moor is intersected with paths and the moon is at the full."