We tell someone they tried their best and that's what matters if they failed something, however knowing you tried your best and still failed is far more demoralizing than failing because you didn't try hard enough, amirite?

Only if you choose that perspective. You can always choose to learn from your failure, try again, and make progress and gain experience - and in that, wisdom. No demoralization required

"That's just like your opinion, man."

i would take pride in knowing i failed but tried my best. a part of growing up is learning you could've always done better.

You risk the demoralization for the higher potential of succeeding. Everything has its price.

Perhaps a more clear & motivating thing to say would be like "You tried hard, but the fail tells us you can try even harder"