If so, it's time to practice receiving compliments! When someone compliments you, simply say "Thank you" and smile back. Do not discredit their kindness by saying "This old dress?" or "I usually can't figure out what to wear".
Receive the compliment and take pleasure in it! At first this will be difficult to do, but it becomes easier as you practice it.
I would like to add...that if you get a compliment from someone, it's now your turn to say something nice (and unexpected) to someone else. Watch out! This behavior will bring a smile to your face, help you make friends with everyone and generally make you feel good about yourself!