Treating it as a fight makes winning the goal, and winning usually means the other person agreed to something they will resent and quietly undo. What you actually need is an arrangement that holds, which means both sides have to be able to live with it. That is a search for information rather than a contest of nerve.

Go into the next one knowing what you need and curious about what they need. Ask more than you argue. If you leave with something that works for them too, you will not have to negotiate it again in a month.