"Mr. Seller, I really want the situation to be a win for the both of us, however I can't promise anything."

"Mrs. Seller, I am going to try my best to see what we can do, but that said I can't promise anything."

"Mr. Seller, I wish I could tell you we are 100% on the same page, I really want us to get there, help me to understand your situation a little better."

Also note that the most important time when you want to practice this is when you know you have a deal in your hands. Super important that you don't become the desperate boyfriend that wants the deal.