Quitting a job can feel like freedom, especially if you get to stick it to your boss on your way out the door. No one is irreplaceable at their job, but it's nice when your workplace makes you feel appreciated. Employees can be motivated with positivity, like raises, bonuses, or even pizza parties. But some bosses choose a cheaper and meaner route: they simply remind their employees constantly that they should be grateful for the work, because the company could get rid of them at any time. Plac…