If you do ever have a dissatisfied client, you have an opportunity. People who are unhappy will tell about 10 other people and then those 10 people tell about 5 people and so on and so forth. Get the picture? So, when you have a dissatisfied client, you have an opportunity to get them to experience your excellent service and to build an even stronger relationship with you. So sort their problem out quickly and they will then tell others good things about you.
Treasure your clients and they will treasure you. Treasure your clients and more clients will be attracted to you, that is how it works!