Emotion is just a normal part but doesnt mean that it would affect luck chance for you to win the game. There's no factor that could affect your winning probabilities.
Yeah it's normal and in general doesn't affect the luck of the games we are playing at all nevertheless I believe that emotions also could become one of the factors to encourage winning probabilities. Why? In case someone is carried away by his emotions while gambling I'm pretty sure his calculations or decisions that he made at the time would be mess up the gameplay particularly in several card games such as BJ or poker with certain decks.
As you say your emotions do not change the probabilities of the games but can surely change the outcome for you if you are unable to control them, if you are a professional gambler and you can actually beat the casinos if you lose control of your emotions then very soon you're going to lose money as well, and even if you are not a professional gambler and you do it just for fun if you lose control of your emotions you could find yourself very quickly in a difficult situation that you were not planning to get into because you simply lost control of how much money you are betting.
in short, it is how you react with your gambling results. but definitely, most games are based on luck and not your emotions. the outcome has nothing to do with your emotions