The idiom that I heard growing up and that I still use is 'Chin Up". I have had to explain what it means to my children. It also is a song topic sung in the 1970's animated version of "Charlotte's Web". The song runs through my head when I say chin up to someone. (maybe a few of you know it??) I think it deals with the physical reaction or representation of shame or dejection. The posture of keeping your shin up is supposed to equate to optimism, but in the image on the site I've attached. the child actually looks to be defiant. I like the idea of deifying shame and disappointment with a posture and an attitude.