Kids ARE very resilient. That's the problem. Therapists know this despite the joke.
As a kid you're so resilient you'll accept anything as "that's the way it is" and so a child will shape their themselves around that world view. Then they grow up with a twisted view of how things are and it requires therapy to unlearn that.
It's like scar tissue on a wound. You healed but you're not quite the same. That wound is now less sensitive to feeling in it's environment and can even be more susceptible to further wounding.