Practicing Mindfulness keeps your awareness of yourself and your immediate surroundings keen. Meditating on your breath, as Zen practitioners and others do, will increase your ability to focus your mind and your ability to make self awareness a habit.
Using The Observing Ego is a similar function although as you get more skilled, it can go deeper. You can get adept at knowing about what your emotions are at any given time, by learning to read your own body energy.
Both of these functions encourage us to have a part of our awareness be located in the body where emotions reside and can be known: if you feel into a sensation in your body and keep your focus “smack dab” in the center of that sensation you will soon be able to identify what emotion that sensation represents. You can test your conclusion by making a simple statement and feeling what the energy does. For example – perhaps you notice a tightness in your throat and a heaviness in your solar plexus ( the area that is located just below your sternum). You say to yourself or out loud “I’m sad about my job” and if nothing changes in your body energy you try “I’m sad about my dog”. When you say the right thing, your energy will drop down and that is the affirmation that what you said is true.