I wish children had more feeling towards others and weren't so selfish!

I do not appreciate the selfishness of children at all. From what I have seen from the bunch of children I've been with, when kids do something they forget about it quite fast. And the problem is when they hurt someones feelings and after 15 minutes come ask you to play like nothing has happened. Today I had a little conflict with my au pair child and I thought to myself, how do I make her understand that she has just hurt someones feelings? Nothing major but just upsetting stuff. I acted like a child a bit and tried to make her notice that I wasn't happy with her but I don't think she got it. If it were my child I would have explained very well how I felt about 'stuff'. Children are so selfish as well and often think about only themselves. I guess maybe they are only too young to understand but still. Make them understand basic things like feelings faster. Agh so annoying. 

And I'm talking of little basic things as well such as a girl going on a play date to her 'friends'. When she arrives, her 'friends' go 'nooooo we don't want to be with her, tell her to go away'. How mean is that seriously? I've seen it all. Also when children talk rudely and disrespectfully to parents and all the rest of that. I know a family who's child ran away from home and when she later returned and saw her crying mother, she simply said I don't care and I'm not gonna tell where I've been and all that. Oh gosh. Not all children are so selfish and feeling less but I somehow believe almost every child has their moments. Definitely waiting till I'm like 30 to have kids and properly ready to put my time to bringing them up.