I, too, left behind some treasures in a former boyfriend's medicine cabinet: Tata Harper Rejuvenating Serum, Laura Mercier Rose Nourishing Oil, and enough makeup to ensure the new girl wouldn't need to run home for her smoky eye palette or lipstick if she were to be surprised with a fancy date night. There's a good chance he tossed them after our breakup — I can concede that I may have overstepped the bounds of reasonable product storage — but I like to think I've been a beauty fairy godmother to his later Tinder hook-ups.And so, a proposal for a small act of sisterhood: When you leave the relationship, leave the moisturizer, too. Tuck it behind the Barbasol and Irish Spring for the next girl to find on a night she'll be brushing her teeth with her finger and sleeping in her contacts. After all, you're moving on to greener pastures — but don't you hope there's some leftover Caudalie when you get there?