I enjoyed this book. I'm glad Andy McNab is on our side and not against us. I hope there's still enough like him in our army and intelligence services.
I think he describes well how he sees the world and assesses decisions very quickly. Kevin Dutton explains the brain science and psychology behind this later.
It seems to come down to an ability to seize an opportunity when it exists, without fear of the consequences for others left behind. In other words the psychopath just does something (often with purpose and planning) without much conscience, agonising or consideration. He or she just sees that "the opportunity is there" and "if I don't take it someone else will." and "it's what has to be done." The psychopath seems to have little or no room for self doubt. This can make for good decisions, but it can also be dangerous in some. It's a more rigorously intellectual approach to decision making, but pros weigh more than cons, opportunities more than threats. In some scenarios getting our feelings out of the way is very useful, in others getting our thoughts and feelings to work together is a saner approach
There's an interesting, and rather different, approach to life described in this book, particularly around making decisions and taking actions. It may not be everyone's way of working, but you can learn a lot from this approach.