It is possible to control your emotions all the time or at least most of the time. People already do that. They do things like make themselves feel angry, sad, relaxed or happy. Controlling your emotions is easy. You are already doing it. The trick is to control your emotions so you feel the way you want to feel. Think about things that make you feel the way you want to feel and breath so you feel the way you want to feel.
The first step is to tell yourself that you are in control of your emotions. The second step is to focus on what you want. I practice feeling the way I want to feel. A lot of people focus on what they don't want and practice feeling the way they don't want to feel.