The 2005 Nobel prize for economics went to a couple of long-time stivers in the field of game theory, Thomas Schelling and Robert Aumann. One central finding of game theory is that cooperation and giving up short term gains leads to greater long-term advantage. This finding is styled as counter-intuitive, but I suspect that to most who spend a lot of time negotiating it seems pretty obvious.
While there are situations that call for a take-no-prisoners, zero-sum style of negotiating, the vast majority of cases call for a more nuanced approach. Game theory experiments show that working cooperatively toward a mutually-acceptable solution, and even sometimes giving up points in the margins, ultimately leads to the best outcomes. How much more compelling is this conclusion in business, where most negotiations involve trading partners who you will deal with again and again?