One of the odd perks of running that I had forgotten is the profundity of thoughts I have while I run. I am a big believer in the benefits of altering consciousness to experience new ideas (I'm probably not supposed to say that), and I think the surge of different chemicals running through your body during running contributes to that sensation.
I've been keeping tabs on my back and legs, given my history with discs and shin splints, careful to not not overdo it. I have specifically been working to note the difference in soreness and pain.
One of my favorite Grey's Anatomy episodes was on the importance of pain. To sum it up, it focused on the fact that medically speaking, pain exists to alert you to a problem. As pain increases, your problem does as well. The inability to feel or acknowledge pain greatly diminishes your safety, both long term and immediate.
The same in running. It's normal to feel tired or sore, but to perpetually ignore pain when it's crying out to you is very foolish. If you don't change or stop what you're doing, you will likely injure yourself.
And such is life. Emotionally, spiritually- pain tells us something is wrong. We listen to the pain, evaluate the source, and treat it. But ignoring will only aggravate the problem.
-"Does it hurt?"
-"Where does it hurt?"
-"Maybe it hurts for a reason."
-Grey's Anatomy (Izzie and Alex talking as Izzie tries to re-enter the hospital after her fiancée died)