How old is the food in your fridge? For your next meal, will you be dining on last night's leftovers or munching on moldy meats and fetid vegetables? How can you tell when to throw something out or save it for another day?
As a rule of thumb, you shouldn't keep already prepared meals longer than three or four days [source: Dakss]. That goes for pretty much all your leftovers, from salads to meatloaf. Remember, just because you put all your excess food in the fridge doesn't mean it won't go bad. Bacteria growth slows in colder temperatures, but it's still there. It's kind of like the difference between speeding down an open highway when traffic is light and driving that same stretch of road during rush hour. The destination is the same regardless of when you make the trek -- all that changes is how long it takes you to get there. Since, in this case, the destination is spoiled food, you want to drag it out for as long as possible, so be sure to stick whatever food you won't be eating into the fridge within two hours after it's prepared.
Of course, some foods fester faster than others. Mayonnaise, for example, seems comparatively impervious to bacteria's drive to spoilage with a two-month refrigerated shelf-life after opening. Baby food, on the other hand, can go bad in as little as a day, so be sure to date any half-empty containers you plan on later feeding to your little ones.
Perhaps most alarmingly, the standard sight and smell test that most of us use to determine if food is good or not is woefully inadequate. Many foods, such as mayonnaise, baby food, casseroles and even pizza may be perfectly rotten but could look, smell and even taste fine. So, if in doubt, throw it out! It's much better to forgo a bit of suspicious, but potentially still delicious, chicken lo mein than to get food poisoning.
Of course, if you prepared a smorgasbord of delicious foodstuffs only to discover that you're the only one eating, you can always freeze the leftovers. Frozen food lasts much longer than refrigerated meals, so don't be afraid to bag up whatever you won't have time to eat over the next few days and stuff it in the freezer.