We all have off days. You had an off day. Take the time out to enjoy your rides.... enjoy more by riding more.

I fell tired... lost energy on a metric century last season. I stopped had an ice cream cone... drank water...and felt fine again. But for only a short while. Then I once again became... almost exhausted. I left the path to ride to a nearby gas station where I got a large [hot] coffee and after drinking it... my energy returned.

I'll never know if I had allowed my core to get too cool... which drained my energy... or if I merely ran out of caffeine. But the hot (24oz) cup of coffee is all I needed to refresh my body.