When negotiating, keep in mind two principles:
1. Know what you need to walk away whole.
Anything else you gain is a bonus. Consider forgoing the bonus because it's important to:
2. Make concessions.
Take into account the law of reciprocity. Neighbors lend to each other with the implicit assumption that - when the need arises in the future - the favor will be returned.
If you compromise on some of what you want this time, you can cash in on your concession next time. Not with an explicit reminder of what you gave up, but with the precedent you set of leaving something on the table.