My first trail race was the Music City Trail Ultra by Hardwin Adventures. It's got a 50k for the hardcore folks. Heather signed up for the 27k, and I signed up for the wimpy 12k version.
It was a ton of fun, and when I got to the 10k point, where I would have to split up with Heather, I wasn't ready for it to end. So, I just kept running with Heather. That was great, for a while. Then a few miles later, I totally ran out of gas. My legs started shaking and not really doing what I told them to do.
I had to let Heather run on without me, and ended up walking about 5 of the 17 miles. But in the end, I did run the last mile or so, and apparently channeled my inner Richard Nixon as I finished.