Meditation is also extremely useful for this. In breath-based meditation, you focus your mind on your breathing and try to eliminate thoughts. Obviously your mind gets bored and you begin to think of other things. Once you recognize that you're losing focus, you simply return to your breath. Over and over. Over time, you gain the ability to view your thoughts and emotions as easily disposable. It takes time but you can actually recognize that you're being affected by emotion, able to let go of thoughts, and be more present in the moment.

It's not hard; you just have to commit to it :)