I can not agree with that. If you say you will leave if ...... then yes you should be prepared to do so. But there are times you should be afraid to (Cautious about saying it) meaning the problem has to be bad enough that nothing else matters. If you are a DIrectv customer as an example looking to lower your bill and you feel they should be doing it for you and they refuse, there are consequences to going to DISH - you may not get your RSN in a couple of areas, they may not have a channel you watch all the time, no Sunday Ticket. Cable may not be good in your area etc etc. Leaving from DISH would have it's own set of things to be considered. (I would pay more with Directv, I would have receivers I don't like as much etc etc) The saying is "Bite your nose off to despite your face."
Both sides never get everything they want in a negotiation. You have to know what's important to you, when negotiating.