I do believe in the hard work ethos.
But then again I do see people who waste many many years of their life- and a lot of money- because they cannot see that hard work on its own is not enough for them to succeed in their field. They end up burned out and damaged, because they can't admit that this particular thing was not for them. They blame themselves for not working hard enough, when they are working as hard as any human being should and their health is suffering from it.
A bit like those Eastern athletes who ended up on drugs because the success culture they lived in did not allow for the attitude of "oh well, I have done all I can but Western Athlete X simply runs faster than me".
My brother gave up his career as a violinist when he realised that however hard he worked he would never make it to soloist rank; his fingers just weren't flexible enough. He had been working several hours a day on his violin since he was a small kid, was now working on it full time and was getting to an age where most violinists start being at their best- so it was pretty clear it wasn't going to happen. He quit while the going was good and has had a successful academic career in a totally different field.
Do I wish he had persevered in the belief that anyone can succeed? He would have been stuck in a second-rate orchestra, on awful pay conditions, still slogging his guts out and still wondering why he wasn't making it. Instead, he managed to come up with a Plan B.
There is a second side to the coin of "you can do anything if you only work hard enough". And that is "if you aren't succeeding you can't have been working hard enough". "If you only push a little harder you can do it". I have seen people have breakdowns because they've believed this. Or high blood pressure. Or threatened heart attacks. Or ulcers.
I want my dcs to work hard because they love working hard. But I'd rather not see them dead from stress before their time.