From a Facebook Post - Sat. March 12, 2011:
I knocked out a 16 mile long run earlier today. At mile 13 I started to feel the temptation to stop. However, the knees and shins were okay, heart rate was good, breathing was steady. So I sucked it up and kept moving. This is where the training kicks in, pushing yourself forward when normal instincts are telling you to stop. Actually taking a moment to be aware of what your body is telling you vs. what your brain wants your body to tell you and taking the correct course of action can be a real trick sometimes. This is also true in the reverse situations when your body is telling you to stop and your brain doesn't want to, and there is no room for ego in either case.