Leaky cup?

How do you fill a kid's cup when it is damaged and leaking from neglect?  I have a son who is all about 'fair'. But only if it is to his benefit and on his terms can things possibly be fair.  He doesn't want things equal,  but things the way that he comes out on top. 
When he isn't getting his way,  there are hissy fits, wailing,  bad moods, defiance and wailing.  My mantra for him for the last couple of years is 'choose joy'!
We watched the movie on netflix, inside out, this week.  Actually I think the kids watched it three times.  I think it was good because I have applied it to his life a bit so far and will continue to do so.
I asked him while he was in one of his funks yesterday if he was making this moment a blue bubble moment or a yellow one.  He knew exactly what I was referring to and said blue. I suggested he figure out a way to make the next  moment yellow so that his day could be filled with yellow rather than red and blue. ..he left the room to think and he actually did turn things around. 
My son's cup had a hole.  I can't repair it.  I can't fill it.  But I do need to figure out ways to teach him to live his life with joy in spite of the leak rather than focusing on the leak and not living life to the fullest.
Pray for his heart and wisdom for his mom.