" Thinking fast and slow" is a self help book by D Kahneman.
According to my simplified understanding of the above self-help book we have 2 brains, which the author calls System 1 brain and system 2 brain.
System 1 brain is the brain that make the decisions, that we do as routine.
System 2 brain is the brain that uses conscious reasoning. I.e. thinking that requires conscious effort.
Now the interesting thing is System1 brain is often making decisions System 2 brain isn't even aware are being made. This is because System 2 brain requires conscious reasoning, and thinking that requires effort. However the interesting point is that the distinction between System 1 and System 2 brains have practical implications.
Having been made aware of this, I believe the quality of my posting has improved because I now usually try to post in System 2 brain mode, which requires conscious reasoning and appreciating the other posters comments, before replying.
To clarify I think most of us enjoy and spend most of our life in System 1 brain, which is for example when we walk through the park and simply enjoy the walk. However if it was late at night and a noisy crowd were in front of us we would then allow System 2 brain to function and consider the risk factors of walking past the noisy crowd.
The interesting point is that I had always thought I had only 1 fully functioning brain (a thought I appreciate many have disputed ) I think however being aware of System 2 brain and employing it more often has greatly improved my life. This O.P was written in system 2 brain that's a nice way to start the day.