Trust me, it's easier to discard some leftovers than to go through a real toilet-hugging, stomach-pumping bout of food poisoning. Cooked chicken should not be left unrefrigerated for more than 2 hours. Less time is better. Make that only one hour if the ambient temperature is very warm. If it hasn't been consumed by then, it should be re-heated or refrigerated. It needs to stay out of the temperature danger zone which is 135°F to 40°F.