Well, first, I'm the one who said the
phrase that caught Sam's attention; specifically, I said " There will
always be someone stronger, better, faster - also younger, more flexible, more athletic, etc. That is the nature of life in general."
I do agree with Sam that too many people make excuses for their lack of effort - and that the concept that there will always be someone physically better is part of that. Too many people say "I won't ever be as good as person X, so I'm going to quit trying". That's why the next thing I said was "The question is, are you better than you were before? In the end, that's all that really matters." Too many people miss this part.
As far as the original statment, (which my instructor says all the time) the rest of it is "therefore, as you get older, you have to get smarter" - and that is a key as well, and not giving up because someone is physically better is tied into this as well - under the idea that (as my instrutor is also fond of saying) "age and treachery will win out over youth and speed"... but that can only happen if you continue to practice and improve your own abilities.
I have students who are younger, stronger, in better condition, taller, etc. - some who are all of these and more - but I know more than they do, and that makes up the difference. Only by continuing to train and improve in some fashion could that happen. That's why they're all afraid to spar me - because it only takes one shot, and I can get that one shot in on all of them, because I'm sneakier than they are - but it took a lot of practice to get there.
So that's the other side, what people who look past the physical see - but too many people don't ever reach that point, and, as Sam said, they quit because Person X is better... and they lose out in more ways that sparring matches or forms competition; they lose the chance to push their own limits, just because someone else's limits are different, and appear better.