Leftovers can quickly become unsafe or spoil. I remember my dad getting upset with me as I would smell everything in the refrigerator before deciding to eat something. I always ask family how long something has been in their refrigerator before deciding to re-heat it. Actually you can't always count on sight, smell or taste to let you know if something is unsafe to eat. We can't see bacteria. The best thing you can do for yourself (and me) is to date leftovers and take a look around your refrigerator every time you are in it and get rid of those leftovers which need to be discarded.