controlling your emotions in gambling is just the start towards a better result in your games but not the end game.
if you want a better series of results you need a good strategy and in many games like sports betting or poker you need a lot of experience to win and controlling emotions comes after this step.
It is easy to say "control your emotions".. As you wrote, it is possible only when you have very big experience, but the amount of bid can distract every player
For me, the most important to control the emotions is a strategy of game, which should be prepared before the game starts.