Left foot, right foot...
As a child/teenager my father would lecture me about taking care of my tools. "If you don't take care of them they will not take care of you" he would say. Of course, he was referring to dull blades on iceskates.
I do math equations in my head when I run. It helps distract me. As I am easily distracted, I usually spend the entire run thinking about the solution to one equation. I suppose I am also not great at calculus in my head. (But really, who is?) I used to tell people that I was "anti-derivative" until I realized that I didn't create that concept. Oh, I like this song.
I haven't been running well since my return. It was an effort and my knees and hip were a constant bother. My shoes were long past ineffective and I knew this. Complaining is for lazy people.
Today I ran. In my shiny new shoes. I ran and ran and ran. I did not think of math. I did not think of other life stresses. It was not until I finished that I realized that my knees did not hurt and that my hip did not ache.
And so my father was right yet again. It's amazing how much your parents learn when you leave home.