“be nice” is a broad rule set. You need rule sets with clear expectations. If your rules are clear, then you won’t feel guilty for banning someone, and they don’t have a good excuse when they appeal. If you choose vague rules, people will submit perfectly good appeals which you have to turn down, and you’ll waste everyone’s time.

A ruleset is a machine. Video games are machines made out of rules, and so are board games. Board games just run on brains instead of microchips. A legal code is exactly the same, just more important. Make a good machine and moderation won’t even require your conscious mind. You can breeze through it according to the process without expending any mental energy.

Spend mental energy judging every situation individually, and you’ll either burn out or become a tyrant. Break your rules, and you either break your community or break yourself.