Can't vs. Won't
Sometimes, precise language can change an organization.
How many times has a broker, or a clerk or a salesperson or some other intermediary (who was just a moment ago being quite helpful) turned to you and said, "I'm sorry, we can't do that."
We can't comp your room.
We can't let you use the showers.
We can't reduce the fee on a very large transaction.
We can't take this car in trade.
We can't give you a raise.
In fact, the correct contraction in each case is "won't."
And once you say "won't" you realize exactly what you're doing.
You're telling a prospect (the most important person in your life, at least in this moment) that your organization doesn't want to accomodate them. Want being the key word.
You're telling a repeat customer (the person most likely to start spreading good word about you) that your organization doesn't want to create an impression worth repeating.
Now, the clerk may believe that she can't change the rules, so for her, it really is "can't." But of course, she started by saying "we." By permitting her to absolve herself of responsibility, the manager is encouraging her front line people to act like cogs, not like thinking, caring people.
There are a thousand reasons you should say no to people. But be honest with yourself, and don't quote the laws of physics or some mythical federal regulation. The same way that just-in-time Kanban inventory systems saved the Japanese car industry, forcing every person in your organization to tell the truth about their decisions will push your organization to do what it should, not just what it feels like.