Diana Duncan 
Hugo the Winner [EPUB ebook] 

The trouble with Hugo is that he is very good at almost everything: sport, school work, making friends … he excels at it all. But his mum and dad worry because he gets really mad when things do not go his way.
When Mum and Dad get him a dog called Barney, they hope he will take things more easily. Their hopes are realised when an accident on a day out leads Hugo to learn that he can be mature and calm when he needs to be for Barney’s sake.
As their friendship develops, Hugo gives Barney lessons about his favourite subjects: orcas, peregrines, and kiwi birds.
Hugo and Barney have something to learn from each other—and that makes both of them happy.