What everyone knows is existing clients are the best source of new business. Yet many developers simply don't know how to leverage the client relationship to make it work for them. Working with vendors I often find that business owners have no idea what it is like doing business with them as a client.

Simply stated: Those who have good customer relations have growing and thriving business.

Those who don't manage or don't know how to manage business or client relations well will constantly fight for new clients.