A happy customer is a returning customer 
When I worked retail, and later as customer
floormat service, I harbored the secret wish that certain customers would never return; in fact I often wished them upon our competitors.
Outwardly of course, I smiled sweetly, said "yes" to everything, apologized to them for
their phukkups, and planned my escape...
...and on the last day at one of those jobs, told my soon to be ex-boss (who had just told me how sorry he was to see me go),
"Remember, the customer is always right, especially when he's wrong."