Last year I saw a 17u coach, who is typically laid back with the occasional snarky comment, completely blow up. It was one of those games where every player seemed to hit to the opposing teams glove and when someone did miraculously get on base it seemed like every call went to the other team.
With about 2 innings to go the coach argued a close call vehemently and got removed from the field and sent to the parking lot. I passed him on my way up to my car to get something and he was calm as a cucumber again and smiling. I asked him if he was okay and he said "Yeah, those types of games are just soul suckers, the boys needed to get a little fire in them, my getting kicked out seemed to have worked, they are rallying." Sure enough, they were. So, my vote is have a coach that knows what their players need to succeed.