Why does it take a Minute to say Hello and Forever to say Good-bye?

Ishmael and the pupil talked about laws that applied to everyone, like gravity or aerodynamics, but they forgot to include the law of death.
“It was a pneumonia that got him-your friend the ape.”
I stood there blinking at him, unable to fathom what he was getting at.
“Vet came Saturday night and shot him full of stuff, but it was too late. Passed off this morning around seven or eight, I guess.”
“Are you telling me that he’s...dead?”
“Dead is what he is, pardner.” (pg.260-263)
I’m not surprised that this law only showed up at the end of the book, because all of their lessons were about the study of life. Nevertheless, with this particular death, I didn’t look at it as I explained in “The looser in all of us”, but in a positive sense. With Ishmael dying, I see it as a green light to go ahead and use all the wisdom he instilled in us, and apply to my own life. Also, it means that I can’t depend in my teachers, but in what they taught me.