Don't listen to these nonsenses. For my whole life I have been eating those types of leftovers without any problem. As long as you heat the leftovers thorough enough, there is no harm at all. Think about people in old days, and now homeless people are eating far less nutricious and a lot of leftovers. But they are still healthy.
健康提醒：这些东西千万不能隔夜吃！