Exceptions can be made but require a trip to the Ministry of Labor (MOL) to explain your situation and give them a good reason why the ban should not be imposed. A company going bankrupt or the owner of the company doing a runner or dying are examples of what might prompt some leeway from the MOL. An employee getting into a fight with his or her boss, or not performing satisfactorily, is unlikely to be viewed with any sympathy, even if they claim their boss was being unfair.
If your boss really is being unfair or you have a legitimate complaint, your first step should be to file a complaint with the UAE Labor Department so that there is a documented record.