In every negotiation, you're in it to "close the deal." You take the best you can get, walk away with it in your pocket, and when the time is right - you come back and try for more. They say the best deal is when everyone walks away from the table feeling they gave away a little too much. The best overview of the subject is "The Zax" by Dr. Suess. Read about the two purists who could not compromise their principles.