Being kind to the rude customer isn’t weakness. It’s refusing to let someone else set your settings.

Staying pleasant with someone who is being unpleasant is not rolling over. It is keeping the controls, because the alternative is letting a stranger in a bad mood decide what kind of shift you have. Anger is contagious and matching it hands them the wheel. Refusing to catch it is a genuinely hard thing to do and nobody hands out credit for it.

When it happens, slow your voice slightly instead of raising it. You are not required to absorb abuse, and getting a manager is always available. Choosing your own temperature is the part worth practising.