I can remember a guy demonstrating a Kirby vaccuum cleaner at our home.
He had clearly followed Sales School 101, because one after the other he shot off benefits disguised as questions anyone in his/her right mind could only answer yes to.
Until that final question... do we have a deal?
No.
He was stumped. He was used to getting a yes. What to do now? But, as you, we vowed to never decide anything major while "on the spot".