The one thing I learned with respect to my own body is if the weather is extreme that day, like super hot or constant heavy rain, then don't do the century and just do whatever the short route is that is around 30-50 miles. Some people can ride in extreme weather; I can't. I've been on event rides where cyclists succumbed to heat stroke and heart attacks; I don't want to endanger my own health, so I am extra cautious on extreme heat days and will ride a shorter route.

As others observed about themselves is true of me also and that is I can't eat most of the stuff at the rest stops. I fill my water bottles with water, add my own electrolyte tablets, eat my own Power Bars and at most I will eat fresh fruit at the rest stop, then potato chips later in the ride if it is getting warm. I've biked with cycling buddies who can eat anything, thousands of calories at one rest stop, and it doesn't hinder their cycling at all, but my body can't eat and digest food like that.