Irony is that you should listen to helpful advice from people but decide the ones to keep. For successful people accepting defeat is definitely not an advice to incorporate.
Is this genuinely the advice you'd give to someone who's less experienced in life? No wonder society is the way it is, most people have extremely low ambitions and then don't even bother working on those.
Maybe an intermediate position is to say, "Before you attempt to beat the odds, make sure you can survive the odds beating you." Because the odds are, they will.
This is more of a question of personal philosophy/mindset, not logic. When you set yourself (or someone else) up for failure you've already failed and at that point there's nothing one can do. If you don't believe you can do something you won't do it. It's a loser's mindset. At the bare minimum you have to believe in yourself to be able to do things, no one else is going to do them for you.
Right, and if someone doesn't have the loser's mindset then reading "it's hard to beat the odds, don't try" wont deter them. So there's no loss there. It might deter someone with the loser's mindset though, and given that they weren't going to make it anyway if you knock them off track early then that's a benefit.
We're speaking in the context of getting steady employment vs taking a very unlikely to succeed moonshot.
Plenty of extremely successful people, including plenty of billionaires, started out with a paycheck with an employer, often for many many years. Plenty more live very comfortable lives. Your framing as the former is somehow "lacking ambition" is just wrong.
The correct advice to give is "don't do it. It's really hard and you'll probably fail".
Anyone who quits after receiving that advice was never going to make it anyway.