The practice of introspection is the art of causing a separation in oneself between the ‘observer’ and the ‘observed’ or, stated another way, a separation of the ‘soul’ (the true self) and the ‘personality’ (the many ‘I’s), at all points in time, as often as you can remember to do so.
Regarding ‘personality,’ the analogy has been given of a container filled with iron filings in a state of mechanical mixture. This container is on the back of a cart drawn by a horse, and every time the carriage hits a bump in the road, the iron filings shift, and the mechanical mixture is different from moment to moment. This is what the personality is like. One minute you've got some bits of personality (iron filings) on top, and the next minute a bump comes along in your life, and you've got other bits on top, and the former ones are shifted elsewhere.
The absolute terror of the situation is that we don't even know we’re like this. We don't know this about ourselves until someone comes along and points it out. And what's the reason for that? Why don't we know this? How can a person live 50, 60, or 70 years without knowing they’re like this? Not realizing they have no permanent state of being that’s not entirely at the mercy of the external events or bumps of life.
Well, if you spend more than half a day in a state of introspection, watching your behavior from moment to moment, it becomes evident that there is no permanence. Yet, a person can go through their entire life up to the moment of death and never have that realization. So, how is that possible? It's not just that they assume they have an ‘I.’ There is something preventing people from seeing it. People can go through life without recognizing the need to do this work. So, they must first recognize a need for it and then act to fulfill it.