You have been doing this since page 1. Now it gets its name and its full method.
Self-observation means watching yourself as you are, in the moment, without judging. It is different from thinking about yourself. You can think about yourself all day and never see yourself once. Thinking about yourself is looking at a photograph. Observing is looking at the living thing.
The tradition calls it a sense, like sight or hearing. In most people it is weak because it has never been used. Like any sense, it grows with practice. At first you notice yourself only afterward: an hour after the argument, you see what you did. With time you catch it while it happens. Later, you catch it just before.
There are three things to watch: thoughts, feelings and actions. There is one rule: do not fix what you see, not yet. The urge to fix spoils the seeing. You only need to see clearly. Seeing, done honestly and warmly, has a power of its own.
Watching is not cold. Watch yourself the way a good friend would, interested and kind. Most people are much harder on themselves than any friend would be. There is no need for that here.