Long progression run hurt until...

I'm following the Advanced Marathoning schedule at the moment. Today's run was a killer, 24 miles progression. That means for the last third of the session I should be 10% slower than marathon pace. My left leg was really hurting from 5 miles and I decided that I wouldn't do the last 8 miles at 6m10s pace because I was tired and the leg hurt. I was on my own until 18 miles and it was tough. I just felt sorry for myself and focused on the rain, grit, cars not moving over enough, etc. BUT then at 18 miles my good training partner joined me and running became easier. yeah, still hard but an easy hard. It's surprised me how much better it is to run a with someone. I ended up doing the pace I wanted. Sweet.