It is madness for sheep to talk peace with a wolf.

Negotiation assumes both sides want an arrangement rather than a meal. Where one party’s aim is to consume the other, talks become a delay that helps only the stronger side, and calling that reasonableness does not make it safe. Recognising which situation you are actually in is the whole skill.

This is no licence to treat every difficult person as a predator, and most conflicts are nothing like that. But if somebody has taken from you repeatedly and every conversation ends with you conceding more, stop hunting for better words. Distance, limits and other people are the tools for that, not more dialogue.