Be the Pond
Picture a pond with lots of fish swimming in it. There's an angry fish, a happy fish, a sad fish and an excited fish etc. Close your eyes and see the fish swimming past you. Turn into the pond. Be the pond. There's no need to do anything with the fish beyond just observing them swim by. Just observe the emotions of the fish without taking them on. You can do this with your own emotions. Eventually the emotion fish will swim away- so will your emotions. Reacting to them won't make them swim away faster- they will go in their own time. Sometimes we forget that we're the pond, and think we are the angry fish. But we are not- we are the not our emotions.
This non-identification with emotions is one of the most powerful ways mindfulness can change us. Mindfulness is not about suppressing any emotion-it is about acknowledging, feeling and holding an emotion in our awareness, without judging ourselves and letting it take control of us.