From my experience, employees take on the attitude of their employer. So when you see unhappy, complaining employees you usually find a boss with the same characteristics. When you find employees that care about what they're doing and have good attitude, you find a boss that cares about his people and has a positive attitude too.
When employees have a complaint, the boss needs to listen and ask for a solution. When employees know that their complaint must include a reasonable solution it changes the whole dynamic. Employees often have great ideas and when you use them you show that you respect the people that work for you.
Too often the owner is concentrating on the work rather than creating a great team that can do the work properly. Sometimes we need to take off the worker hat and put on the owner hat, and manage our people with the same enthusiasm that we manage the work. Yes, in the heat of battle every day that is challenging, but that's why you're the boss!