What Does A 1/2 Marathon Feel Like?

With my first half marathon less than a month away, I decide to run 13 miles today. My non-runner friend is surprisingly willing to join me, so I set our pace at a leisurely 12 minutes per mile with planned stops around miles 4 (Palos Verdes High School's cross country course), 7 (my mom's house), and 10 (my friend's house) and choose a route that is mostly downhill until the final two miles. We carry water and consume gels or shot blocks at each break.

My friend starts feeling his knees around mile 7 and, when we reach his house, decides he has had enough. I realize my legs do not have enough strength for the hill I must climb to get home, so I decide to save myself for an attempt on a later date. 10.66 miles is nothing to sneeze at, easily both of our longest runs ever, but I still do not know what it feels like to go the distance. I doubt I will be attempting 13 next week since we will be attending an auto race in Monterey. Hmmmm....