Happiness is a choice just like choosing which brand of cereal to pour for breakfast or what you'll wear today. You have the ability to choose to be happy. If your feeling those good and positive emotions and something negative happens to you, then you're faced with a choice to control your emotions or be bested by them. How you respond to a situation is in fact within your control. You can't ask the universe to change the situation, the universe responds to the energy you put out to it.
You certainly can't ask a person to change because its not their issue that you feel the way you do. Regardless of the scenarios when faced with challenging situations or individuals its how you choose to respond that affects your vibrational flux. When your anything but happy or content it becomes your job and your job alone to redirect your focus to getting yourself back to happy. The universe isn't going to do it for you and regardless of what a person may say or do the choice remains you can be affected by or you can overcome it by choosing to be happy. Nobody can give you the answer as to how you can control your emotions and keep them positive. You have to figure that out for yourself, because it'll be different for everyone.