As you mix and shape your burgers, the heat from your hands causes the fat in the mixture to soften and become sticky. To avoid having the meat stick to your hands and prevent overworked tough burgers, try to handle the meat gently and just cup your hands around the meat as you shape it into balls. To further prevent a sticky mess, you can rub your hands with an ice cube or dip them in cold water before shaping, or coat your hands with oil or cooking spray.