When you are going through a breakup it's important, for your self-esteem and self worth, to feel beautiful. It may seem materialistic but feeling good about one's self will help boost your overall demeanor.
Feel free to take an extra ten minutes to do your hair or your make-up. It's okay if you decide to buy a new outfit too. Give into these small indulgences, so that you can feel better about yourself. It's not superficial, it's something only a breakup can justify.