Do you have airtight containers?
Avoid storing your food in its original container. It exposes it to contamination and, it doesn't help keep the food fresher. Therefore, invest in some good airtight containers that you can be preserving your food in.
Is your fridge cool enough?
You also need to make sure your fridge is set to the ideal temperature for your food to last longer. Make sure that it is cool enough and in case your fridge is faulty, you will probably need to consume any leftovers faster.
Things to note:
To make it easier, put labels every time you store food in the fridge. It's often easy to forget the exact date when you put food in there so this would help avoid any confusion.
Also, if you're not sure you will be able to eat your leftovers within four days, simply put them in the freezer right away. The flavor might not be as rich over time but, it will still last longer in there as compared to the fridge.