One of my favorite blogs to read is the blog by Seth Godin. Recently he wrote a blog about looking for opportunities to say "yes." Here is the blog entry.
This really rang a bell with me. All of us that have customers - and that is all of us because if we don't interact with an external customer we all have internal customers - need to look for ways to say yes. When I am working with a customer that I click with, they almost always see me as a person who fixes problems. When something goes wrong, I find a way to fix the problem. I have heard many stories from customers that have used my competitors and the other company is not quick to fix the problem.
Looking for ways to say "yes" is a much more enjoyable life than looking for the ways to say "no." Monitor your words and determine to look for more ways to say "yes" and when you hear a "no" from your mouth, quickly perform the fix.