(Pro 30:10 KJV) Accuse not a servant unto his master, lest he curse thee, and thou be found guilty.
In modern times our intellectual side does not believe a “curse” (7043) has any power. The problem is that we have a non-intellectual side that is open to superstition. How often have you had someone say, “Knock on wood”? How many people do you know that are a bit wary on Friday the 13th. The Bible admits that curses exist but seems to tell us not to worry about it. Even here we don’t see what we think of as a curse.
The Hebrew word is fairly common but has many different translations. The root meaning of the word has to do with making things slight, quick or of no account. Here we could get the idea of someone trash-talking about you. Aside from the general sense of showing courtesy to people and avoiding gossip is the warning that even people with no obvious power over you have the ability to caste doubt on your character.
So? If you can’t be kind and courteous because it is the right thing to do then maybe you should consider it as a means of self-preservation.