I have no experience with younger wrestlers because my son only started wrestling as a Freshman. Once during his first season, his match came up sooner than expected and he was not prepared. He wrestled poorly and lost. He shook hands, but then threw his headgear as he walked off the mat. When I criticized his behavior, he told me his coach liked them to be "fired up". I told him very clearly that regardless of what his coach liked, his Mom could and would sit him out if he acted like that again. He still doesn't like to lose, but he's never shown poor sportsmanship again.

I also notice many experienced and successful wrestlers are able to show good sportsmanship on the mat and then after the formalities, they quickly leave the arena where they can then vent in private. I think this is fine and shows self-control and intensity.