This is nonsense.
No one achieves by themselves.
Encouraging people, especially young people, to see things that way makes for a very self regarding, selfish society. It also makes them lonely when things go wrong, as logically, that achievement is theirs alone too.
In your child's case - were there parents who provided a safe, healthy home, food in the fridge, a roof over their heads, wifi, and so on.
Were there parents who expected their children to go to school, behave, engage, study, apply to university and get on in life? That expectation is belief in the child, so that builds a confidence too. And on and on with every aspect of a child's achievement.
Of course, the child does achieve, they rise to meet the challenge, they apply their own resources to a good outcome, they accept the bounty bestowed on them. They most certainly achieve, but it is most certainly not in a vacuum.
All of us get help, and we need the young to recognize that.
I am probably hard in my post but, truth be known, my lovely dog died today and I feel so sad, so excuse me?