Belief in a cruel God makes a cruel man.

Whatever you place at the very top of things, you will slowly come to imitate. If the highest thing you can picture is harsh and keeps score, then harshness begins to look like maturity and mercy begins to look like weakness, and you will find yourself handing that out to the people near you. The same works for anything else put in that position: a philosophy, a market, a rule inherited from your family.

Look at what you treat as the final authority in your life, and ask what it teaches you to do with people who fall short. If the answer is contempt, that picture is worth examining.