Emotions during a pool match are negative and the sooner you learn to set them aside, the more advanced game you will play.
Emotions take over your subconscious thoughts and suppress the ability to let your stroke out and tackle the task at hand.
Sure, anger will sometimes force you to bear down and fire, but more often than not, it's an excuse to lose. ( I couldn't play my best game because of the sharking.) That's why sharking for some, is so effective.
Emotional turmoil is a form of sharking. Tossing a break cue, cussing, slamming things around. If it wouldn't be tolerated in a tournament and ruled "unsportsmanlike conduct" then why do you tolerate it?
Unless your last name is Strickland, you can't force out emotion and grab pinpoint concentration easily.
Hecklers from the audience are just as bad. One time I was playing a tournament match and had a heckler seated in the bleachers only a few feet away. He would wait until I took my final backswing before he would say things like "He's going to dog it." I asked him 3 times to stop and he wouldn't. I went and got a large steaming black coffee and from beside the table I told him if he opened his mouth one more time, he'd be wearing the coffee and if he didn't think so, to just say something now. The bleachers around him emptied in less than 5 seconds. He shut up the rest of the match. Nobody would sit near him after that.