2 years ago, 40 mile ride...20 out, 20 back. 90+ degrees with a bunch of hills. Was feeling pretty pooped by the turnaround point and had to ride about 5 miles back to a gas station to get more to drink.

Stopped there, refilled bottles and just sat down...totally spent...at the bottom of another hill (maybe only a mile long, but about 9% at the start, maybe a couple hundred feet) feeling like I was sitting in an oven at the base of everest.

Finally got back on and struggled another 10 miles or so. About 5 miles from home, had to get off and sit in the shade again. Finally 3 miles from home had the choice of going up one more hill and coasting home, or cruising rollers back. Decided to do the hill and then literally stop pedaling for the last couple miles. Bad choice. Got halfway up, had to lie down (no more sitting for me) on a rock wall for about 10 minutes. Finally got to the top and coasted home.

Scary stuff. Did the same ride a week earlier with no problems and a few days later with no issues.

Sometimes you just have a bad day.