[Kaslin]

Many years ago when I was a teenager, I watched a movie in Germany where I grew up (I am a naturalized citizen who immigrated legally in 1966) that was called: Vater werden ist nicht schwer. Vater sein, dagagen sehr. Meaning: It not difficult to become a father, but to be a father is another story.

[Night Hides Not]

Here's an old favorite of mine, from Ambrose Bierce:

A son does not learn how to become a son, until he becomes a father.