Occasionally problems will occur. When it happens to your customers, fix the problem fast. Make it your speed and generosity that gets remembered, not the problem.
First be effective and then be efficient.
If they're going to remember the problem, make sure they remember it fondly.
You do more for yourself when you forget yourself.
Instead of just asking 'How did I do?' ask 'How can I do more?'
Make your upper limit, no limit.