Burn-out is often a mixture of anger, frustration, and depression. Each person has their own limits of those feelings before burn-out sets in, and each person also has a limit of how many hours they can work productively in a week.I've known managers that drove themselves to "work" over 60 hours per week, however, the effectiveness of that work was pretty bad. To a man, they didn't recognize it until they had been forced to step back and relax for a few weeks. Cut back on your hours if you are working anything over 45 hours per week, and slowly work back up to the level where you and the company are comfortable.
Write down obtainable goals for each shift you work and check them off as you do them. Do the same for your staff. Get rid of anyone on the staff who isn't willing to work and do their job effectively.
As for people not being satisfied, you need to jump a big hurdle. The best managers are not as concerned about what other people think as the way they measure up to their own internal standards. This is self-actualization, and it can't be done as long as you look to others for approval.
Examine why the people aren't satisfied, determine whether or not it is something you can control, then if it is, do so and arrange a method that the problem will stay "fixed" without your continuous intervention. If, after examining the situation in detail, you discover it isn't within your control, tell the person "Bite me!" or ignore them.
Some "management" types manage by setting impossible standards and goals. New managers often buy into this and get flustered and upset. The old managers recognize the complaints for the crock that they are, and sometimes feed the same type of stuff back as a joke. Example: "Did you know we cut our toilet paper costs by 70%? We did it by lowering the jumbo dispensers to within seven inches from the floor. People have a hard time getting it out, and don't bother unless they really need it." Depending on the smarts of the oppressive supervisor, it'll get a big laugh, or everyone in the circuit will get a memo from the one-upping supervisor "Lower your toilet tissue dispensers to within six inches of the floor."
Sometimes the impossible tasks given by a supervisor are because of other reasons, like fear of their own job security or an active attempt to force a "quit." In thse cases a confrontation is often required to clear the air, and sometimes it is best to get a different job.
As for customer complaints, and burn-out from those complaints, I sympathize. Only getting out of the service industries, having a VERY understanding supervisor, or becoming your own boss will cure that.
Now that I don't have to worry about a theatre customer going to my boss, I get perverse enjoyment (as a customer) out of walking up to any other theatre customer who is being an ass to a staff member or manager, and telling him in detail how he's being an ass and making life miserable for people trying to serve him. Paybacks are hell.