Protecting yourself should not require becoming cruel.

There is a version of self-protection that hardens into something meaner than the thing it was defending against. It happens gradually, each sharp response justified by the last injury, until the harshness stops being situational and becomes how you are. Protection was supposed to preserve you, not replace you.

When you set a limit, aim for clear and unapologetic rather than punishing. Ask whether you would be comfortable with the way you said it if you were calm. Firm and kind are compatible, though it takes practice.