“I am an Engineer…”
General nature of human is to associate or identify with some thing or other. This is called ‘Athma Vismruthi’. Without identification, there is no movement or change in mind. Crux of samsara is bondage or identification.
What exactly happens when I say ‘ I am an Engineer’. First, I have to create a person out of me and add all attributes (samaskara) of an Engineer. This activity has to be registered in our chith or memory. When there is a registration, it is categorized either into raaga or dwesha. This impression continues in day to day life and becomes part of ‘I’. Here is a person born out of identification.
When we closely watch our mind, there is constant change in personality based on the situation interacting with others. During office hours you are an engineer, after coming to house you are a husband, while playing with kids as a father. Hence, something which changes time to time cannot be our true nature. It is very important to realize that the entire persona or stack of personality hangs in the thread of memory. A person who has lost his memory can never become the same person again. This is an amazing phenomena.
Looking from other angle, what happens to this person when he slips into sleep. It is very important to understand three avasthas.
Read : Avasta Triya