HARRY
I need your help. I need your advice. Bane says Albus is in danger. How do I protect my son, Dumbledore?

DUMBLEDORE
You ask me, of all people, how to protect a boy in terrible danger? We cannot protect the young from harm. Pain must and will come.

HARRY
So I’m supposed to stand and watch?

DUMBLEDORE
No. You’re supposed to teach him how to meet life.

Harry Potter and the Cursed Child - Chapter 2 :
See this quote in the Pensive -