Ran cross country in high school. Didn't take it seriously, and was never any good. But I enjoyed it.
Decided to do a marathon my senior year in college (1978). Didn't know what I was doing but got up to about 40 mpw and struggled home in 3:30 or so.
I've been running pretty steadily ever since, for a long time my mileage stayed steady at between 2,000 and 2,500 miles per year. Got a little more into it when I was around 45 (children were also older, which made it easier), and upped my mileage to the point where I've run over 11,000 miles in the last three years. This year, I've been struggling with a calf problem, and it looks like I won't even make 3,000 miles for the year.
It's still fun, though. One advantage of never having been fast is that I still have a chance at setting some PRs. I set a marathon PR last December at age 48 (2:57). As my kids would say, "it's all good."