The human race is a social construct make up your own reason for continued existence and happiness and try and commit to it.

Maybe there's nothing to "say..." Maybe all that's left to do is listen. Listen unabashedly. Let them share their darkness... sometimes that helps more than anything. Beyond that, I strong recommend medication. If this is a biological thing (and it often is), then what's necessary to treat it biologically, and then add the counseling on top of that.

A lack of motivation could be due to a chemical imbalance in the brain. I would suggest seeing a psychologist or something to check if that might be the case. That someone might get back their motivation and do a little good in the world. Even if it just has a small impact, helping others is always worthwhile especially considering all the greedy stupid people in the world.
Oh yeah and there is no "finish" and maybe not even a race. It is an ongoing struggle that makes no sense anyways. So why not try to make the best of it?
If all of what I've said doesn't convince them, I won't judge. Everybody should be able to make their own decisions about quitting the "race".

I would tell them that i feel their pain..It's a difficult thing to constantly feel as if you make no progression whatever you choose to do with your life..But human will is a daunting thing, and will only be temporarily stifled in most of us...I fall down a lot, but I get back up..slower than when I was younger, but I try to be positive about myself, if I can't always feel that way about the rest of the world..

I generally tell peple tha tit doesn't really matter so much how they measure up compared to anyone else, because there will always be someone better. It is better to use your own past performance as a measure comparison. I tis a more honest way of measuring actual improvement.

The only real goal anyone shoudl have is to be better (on average) than they once were. If you also happen to outperform others, that can be a bonus, but should not be a person's main focus.

Take a nap...

Your choice.
I'm not going to judge.

What sort of race? Do you mean in the middle of it or before they even get started?

"If you're gonna start it, might as well finish it. Let's do this!"

Find something else to motivate you.