Maybe try channeling the emotion into a different activity. The typical example is if you feel really frustrated or angry, take it out on a punching bag.
Letting negative emotions take over your communication isn't great because you may "lose control" and reveal more than you intended to.
But sometimes, losing your rag and speaking your mind is not only very healthy, but it can also help push a situation in your favour - or at least express exactly how strongly you feel about something.
If you're adamant you need to control these emotions though, then maybe a timeout or some breathing exercises whenever you feel the urge to let your emotions run riot might be a good idea!