“cursing you.” There are several words translated “curse” in the Old Testament. The one used here in Ecclesiastes 7:21 is qalal (#07043 קָלַל), and its root meaning is “to make light of, make of little account, treat as insignificant.” The semantic range of qalal ranges from just speaking badly about someone or “making light of them,” to genuinely putting a curse on someone. So “curse” can mean just badmouthing someone. For example, the CJB has, “Also, don't take seriously every word spoken, such as when you hear your servant speaking badly of you.” The TNK has the final phrase as hearing “your slave reviling you.”
Life is difficult and all of us say things in the heat of an emotional moment that we did not really mean or think through, as Ecclesiastes 7:22 says. So we cause ourselves a lot of problems and endure much emotional trauma if we do not learn how to ignore and/or let go of things that people say and do. If we take to heart everything we hear people say about us, we will have nothing but worries and bad days. When we make a mistake or say something unkind, we are happy if other people ignore it and let it go, and we can have a very peaceful life if we learn to do that too. We will never have the “peace that surpasses all understanding” (Phil. 4:7) if we are offended by everything that people say.