Being able to navigate through these circumstances without losing or damaging a relationship requires perspective, focus and patience. Perspective is perhaps most important. A client may be more demanding and less reasonable can tempt even the most even-tempered person to set a client straight.
In my experience, the old proverb that "a soft answer turns away wrath" is great advice. In other words, arguing with a client is only going to exacerbate the problem. This is not to say that one's position shouldn't be made, just that how and when it is made should be carefully considered.
Don't respond immediately. When a client incorrectly criticizes, accept it. Wait before you defend. Acknowledge the criticism without acknowledging guilt. At a later time, you can give your perspective of the situation. Generally, the client will have had time to get over the frustration they were feeling and consider your point of view fairly.
Check your feelings. If times are especially tough for your business, try to remain positive for the sake of your employees and your clients. No matter how good you think you are at hiding your feelings, people can read fear. Don't let fear have a place in your psyche. Take one day at a time. Don't picture disaster, picture victory.
Communicate openly. Share as much of your business situation as possible with your employees. They will stick with you through more than you can imagine if they believe you are doing what's best for everyone.
Make up lost ground. Eventually all of this mess will pass and business will be good again. Your employees will expect you to make things right for them as well. If you have put a freeze on wages, don't let it linger after business has improved. You'll pay a huge price in replacing valuable employees if you do.
Go the extra mile. Clients should always get great work and great service, but that goes double during hard times. Don't underestimate how much your extra effort will be rewarded, or how your lack of effort will be punished.
This is a relationship business, and relationships are hard work. Don't fool yourself into believing that a client appreciates how valuable you really are and don't fool yourself into believing you are more valuable than you really are.