Both of our sons went through a phase of showing inappropriate emotions on the field. Yours may only need some advise, but simply talking about it didn't seem to change our guys' behavior. So....this is what I did.
First, I made them write an essay about the problem and how they were going to fix it. They were grounded until it was done. Then, I taped the essay on their bathroom mirror for the rest of the season. Finally, I told them I would pull them off the field immediately if I ever saw it again. Sometimes I had to get up and stand by the fence to remind them to keep it in check. They still laugh about it to this day, but it worked.
