My good friend's dad did one of these when we was in his fifties.
You are typically allowed to have people pace you (run along with you), so my friend ran with his dad from the 60 mile point to the 80 mile point. I remember my friend making a comment that sounded to me as the most ludicrous thing ever. His dad was really struggling around the 75 mile mark. His comment was this:
"Dad, I know this is tough, but there is really only 5 more miles of hard terrain. After that its just 20 easy miles."
"It's all downhill from here!" is a very common encouragement called out by spectators at road races. I've heard it said by persons who could have looked back and seen that they were at the foot of a long uphill grade.
"I write software" is typically where I start and if the other person wants more information we can go down the rabbit hole from there.
Funny story though, my wife and I are friends with Eric Meyer (http://en.wikipedia.org/wiki/Eric_Meyer) and if we're in a group and other people ask him what he does, my wife jumps in and says he fixes printers. You should see his face :-)