Looking at the leftovers you have in the fridge, you just never really know. According to Katherine Zeratsky, R.D., L.D., leftovers are actually good for three to four days. However, she says that if you know you can’t eat them in four days, you should be sure to freeze them. It is best to keep your food in temperatures under 40 F if you aren’t going to eat them. Zeratsky says that by keeping foods in temperatures above 40F for extended periods of time, or leaving food in the fridge for longer than four days, you run the risk of getting food poisoning. However, when you are ready to eat the leftovers, you should cook them in the stove, in the oven, or in the microwave until the internal temp is at least 165 F to kill off any bacteria. Raw foods should not be kept out for longer than 2 hours at room temperature.
In an article at My First Apartment, they suggest avoiding cross-contamination, as well. This means avoiding using prep items, containers, and surfaces that have touched raw meats to prepare other food. It is best to keep things separate, and to heat raw foods to at least 125 F if it’s beef, and at least 165 F if it’s chicken.
The article also suggests keeping the refrigerator organized so that you know how long food has been kept in the fridge. You can do this by either putting food in special containers, or by placing a label on it so that you remember. It’s also a good idea to avoid tasting the food to see if it’s still good, and to throw it out when you aren’t sure. As Zeratsky explains, bacteria will not usually change the taste or smell of the food.