You've all been very helpful with your responses, thanks!
Noah, good point you make there. My problem is that I perform mostly for friends and family. Recently, I've been performing for my NEW girlfriend's family members and they've never seen close-up magic before. Their reactions to the effects I have shown them have been quite soothing to my ego to say the least.
However, they usually want me to repeat the same effect for someone else who didn't get to see it at that very moment. I don't want to repeat the effect for the same person but I don't want to come off as being too cocky and I don't want to shoot off some corny line like "I would but then I'd have to kill you". Any more suggestions, please keep them coming!