If you want to keep your promise you should Underpromise and Overdeliver. The First Law of Customer Service is Satisfaction = Perceptions – Expectations. The Second Law of Customer Service is it's hard to catch up once you are behind! When you over promise and underdeliver you are raising your patient's expectations which is setting up a trap that you could eventually step in. If you under promise to lower their expectations and then over deliver with a fantastic experience you will satisfy your patients by successfully managing their expectations. You should always keep your promise but if in doubt, under promise and over deliver. When a patient breaks their front tooth off and asks you if you can match it, why would you say absolutely! I tell them God made the tooth next to it and you want me to match it?!? I will try my very best, but no one can perfectly match your natural human tooth. Their expectations have been lowered and then they are delighted when they see the final result because I exceeded their lowered expectations. The same with post-operative pain; will I feel any pain afterwards and can I go back to work? I say, "When the anesthetic wares off you're probably going to want to jump off a cliff." When they come back in, they are all happy saying, "I was fine afterwards. That didn't hurt at all." Then I tell them they're probably married with children and they're used to pain and suffering, they chuckle and we're all good. At the Fortune 500 level they almost never pick an extrovert salesperson for CEO because that person has spent their entire career over promising and underdelivering and that never works from the top. They always want an introvert because they listen, think, and then methodically set out with a doable plan.