It's during dream sleep where we start to actually take the painful sting out of difficult, even traumatic emotional experiences that we've been having.
REM sleep takes the painful sting out of difficult emotional experiences so that when we come back the next day, we feel better about those painful events.
For some kids, it takes the sting out of reading to put Sting in it and now that he's bound for many hours of page-turning, Sting is at a lost for words.