The strongest negotiation sometimes ends with both sides protecting the relationship.

Sometimes the best available outcome is that both sides step back from a point that would damage the working relationship. It looks like nobody won, and what has actually happened is that a longer-term asset was protected at the cost of a short-term term. That decision requires both parties to see past the immediate item. It is more common in good negotiations than in dramatic ones.

When a dispute starts costing more in goodwill than the item is worth, say so out loud. Propose setting it aside. Naming the tradeoff is usually enough for both sides to take it.