Often we think of onaas devorim of not saying cruel things to people as referring to big things, like tearing someone down in public. In reality, its much more subtle. People hurt each other with callous remarks all the time. And usually, they didnt even mean to.
Those callous remarks cost. Even when we forget what weve said, our victims dont, and neither does HASHEM. He makes sure well feel the after-effect one way or other.
This Shmuz will heighten your sensitivity to your fellow human beings and keep you from stumbling into the ever-present trap of saying the wrong thing.