The Control Panel of X-Author Contracts allows you to reject the changes made to the smart fields in your agreement document with just a right click on the smart field. This is applicable when you want to negotiate only certain part of your agreement document without changing the rest of the content.

Also, if there are multiple occurrences of the same smart field in a single agreement document, but with different values, you can decide a single value for that smart field for all of the occurrences across your agreement document.