Well, it can.
Boxing is an art. It is about hitting and not getting hit. It is not about who can get worked up faster and fight with blind rage. Never was the old Samurai Maxim truer than in boxing:
“The angry man defeats himself in battle and in life”
Emotions waste energy. You will learn that to survive in boxing, you must detach from them. Remember, hit, and don’t get hit. That is what you need.
Boxing also teaches you about control, when to hit, when to not hit. As I mentioned, by separating your emotions from your energy level, you learn to control and can act when necessary, not when your feelings let you. Boxing also desensitizes you to getting hit. You learn not to panic or get frighten to being struck. A good thing to be sure.
You may also wish to check out another art to compliment boxing, something that helps strengthen you mentally. A good Tai Chi Chuan class or an Iaido class can help you learn to relax and control your emotions. Very valuable skills IMHO.
"Let your food be your medicine, and your medicine be your food"