Something we all want is customer satisfaction. Customers are the reason we are in business. Whether you are a consultant or a retail business or an artist or writer...you are doing what you do (because you love it..hopefully) and ultimately you are hoping someone else will too so it is important that you place "value" on your customer to be sure your attitude matches.
It has always been interesting to watch clients manage their customers. Some work very hard to provide high quality products and services and get very few complaints. They are enthusiastic about their business and value their customers. In fact they proactively seek out feedback so they can continue to provide top service or products. However, there is a fraction of businesses that perhaps have gotten tired or are struggling and their anxieties & fears come through when their customers complain. I have witnessed business owners getting very angry and critical of customers who dared to complain or voice dissatisfaction. They respond in a combative manner and suggest to the other employees that the customer is the "real problem" - this is never a good sign on many levels. Note to reader: if you find yourself feeling this way about your customers...it's a good time to step back and consider talking with someone about these feelings. It means that there's something else going on that needs to be addressed.
Some customers or clients are absolutely demanding and hardly enjoyable to deal with but there are ways to manage these people and create a win-win result. In some cases it may be time to fire a customer because no matter how hard you try they are not going to be satisfied. The key is to know when you've reached this point.
Here is an article that will hopefully be helpful to you with customers issues Handling Customer Complaints. It's always good to consider the many options available and to check your own attitude regarding these ideas. Remember, getting a good result has as much to do with your personal feelings and attitudes as it does with the person in front of you complaining. Remember, it is a good thing that they came to you because they are giving you the opportunity to fix the problem. Unfortunately for every one that comes to you there are probably some that don't but if you 'listen & learn' from these folks, you are minimizing further issues going forward.