John Lennon talks about Instant Karma, that should apply to everything in life. If you are nice to people they will be nice to you.

If you are nice to a client, the client will be nice to you. If you are nice to to the guy next to you in traffic, he will be nice to you.

Just remember:

Instant Karma’s gonna get you
Gonna knock you right on the head
You better get yourself together
Pretty soon you’re gonna be dead