Your friend sounds like a jerk. If you participated in the Olympics and didn't win a metal, you've still participated in the Olympics. I suppose you could argue that hopefully if you're participating in the Olympics you believe you have a chance of winning, but the outcome of an interaction (or event, since I don't think we can call races 'interactions' per se) is not the only thing that determines what that event was.

In a given race there can only be one winner (or, let's say 3-4 since we'll allow room for first, second, third place and maybe a tie). So invariably most of the people who run the race are not going to win. Anyone with any logic knows that. Additionally, if you pay attention to local races or just the times of other runners, you'll know what's on par/really good and what's not. That doesn't mean that if you aren't the best, you don't achieve anything.

It's like saying "If you write a book but no one wants to publish it you haven't written a book." "If you run in a race but you don't win, it isn't a race." I wasn't aware that our achievements are measured only against other people and their opinions.

I say, good for you for running, and your friend sounds like a glass of sour milk. Please don't take his discouragement to heart!