Them: "You're so beautiful!" You: "Shut up, I don't believe you."

Instead of accepting one's genuine observation at face value, you tell them you think they're full of it. Sure, you're on the lookout for ulterior motives, but when you get right down to it, you just threw someone's compliment in their face, put them on the spot, made them feel like they don't know what they're talking about, and... Do you realize you're just begging them to justify their viewpoint? In its most innocent form, such a compliment is not presented to you, for you to evaluate, comment upon its accuracy, and ultimately reject. Think beyond your insecurities when this happens. You'll go places. So I want to know, why don't you respond the same way when someone tells you that you're wearing your shorts inside-out? Or that those shoes looked really cute beside your earrings? Alas...