Walking away from a negotiation

Most of negotiations in my class have resulted in an agreement. But, when executive education students do the same exercises, few of them make deals. My guess is that this is because in a classroom setting it's easy to decide to take a deal as long as it's better than your over-simplified BATNA.

But, if these were real deals, I suspect that people would care about more than just the monetary value because they would have to work their counter party after the agreement was signed and during future negotiations. So, trustworthiness would be valued more because fundamentally deals are about relationships.

I want to get better at walking away from deals, even if the artificial classroom environment is encouraging me to reach an agreement. I'm worried that this is forming bad habits; reaching agreement isn't necessarily a good default.