It's only because.

Sincerity is a virtue.

You can't constantly mock everyone that cares about you, then act like you've never done someone an injustice.

You can't blow up over one misunderstanding at people that care about you more than you understand.

You shouldn't call your good friends assholes in a place where everyone can see it, but they'll still love you anyway.

Don't leave someone a voice mail mocking them, with all their friends laughing in the background.
It's hilarious at the moment, but it isn't kind. No one wants to get one of those.
It doesn't make anyone feel good about themselves.

If you can't let the small things go, like a change in dinner plans for whatever reason,
how will you ever let go of the big things?