Your in-laws comment that "you're looking healthy" and you realize you better up the mileage because you must be out of shape.
Your grandmother asks "are you sick?" and you smile because it means you are really good shape.
You tear up at the end of the movie Endurance.
You know every note of Chariots of Fire.
You see signs on the highway saying how long it is to the next town and you do the mental calculation about how long it would take to run there.
You forget that the Olympics have events other than track and the marathon.
You would actually watch marathons live from start to finish on TV.
You know how far a 5K, 10K and marathon are in miles, including the tenths.
The tenths are important.