Thank You

I know I may be out of my mind, but what is the deal with people not saying thank you? Saying Thanks and your welcome is one of the basic common courtesy. It makes me just want to punch people out when I hold a door or go out of my way to be courteous and I don't get a THANK YOU!!!!! Everyday this happens it makes me want to be just as rude as the people around me, but I refuse to stoop to the rudeness level.