You don’t have to be loud to have principles. Most principled people are just consistent.

Announcing a standard is easy and keeping one is not. The people you actually trust are rarely the ones who talk about their values. They are the ones whose behaviour is the same on a bad day, when it is inconvenient, and when nobody important is watching. Consistency is the whole of it, and it is almost invisible from outside.

Choose one rule and keep it without mentioning it: you do not repeat things, you pay people back the same week, you say when you cannot do something. Hold it for a month with no commentary.