The energy you put out into the world always comes back to you like a boomerang. If you’re callous and insensitive about the people around you, you can be sure that, at some point, life will send that same energy back to you. Next time you experience behavior that feels hurtful, look for where you may have (unconsciously) behaved in a similar way. Whatever you do, don’t keep that energy going.
What goes around, comes around.