What is meant by this sentence, " child is the father of man"?

In the poem "My Heart Leaps Up When I Behold", the seventh line is "The Child is the Father of the Man".

This simply means that becoming a Man does not rely on age but also on the habits, principles, and values one learned as a child. Therefore, a child flourishing in an environment where he manifests healthy attitudes and positive traits and characteristics will grow up as a well rounded individual.

Man is a product of his childhood experiences.