Cooking meat causes the juices to go toward the center. By resting the meat, you are letting the juices redistribute throughout the meat again. It’s the juices that make the meat more tender and juicy when you eat it. Cutting into meat right after cooking causes all the juices to run out, resulting in the meat being tougher.
I finally had the idea of cutting an empty egg carton apart and saving a portion of the end that can securely hold our leftover eggs. There is no room in the space in the refrigerator door where the egg carton fits, but there is extra room in the butter drawer. We know to use any eggs stored here first, as they are older.