Here's a summary of Chapter 3 of Principles, titled “Be Radically Open-Minded”. Or as I like to put it: “Ways Your Brain Sabotages You, That Bloody Thing”.
Dalio opens by saying this is “probably the most important chapter, because it explains how to get around the two things standing in most people's way of getting what they want out of life.”
The solution to both these barriers is to be ‘radically open minded’, a phrase Dalio uses to refer to a very specific way of thinking.
It's easiest to think of yourself as having two ‘yous’. There's a conscious part of your brain that reasons rationally. And there's the subconscious part that reacts defensively and simplifies; offering excuses and blaming others when you screw things up. When you face criticism, this is the part that reacts in anger, even if intellectually you know that constructive criticism is good for you.
You should feel your ego barrier intuitively. If you've ever seen someone “angry at themselves”, this is their higher brain fighting with their low brain. To use a personal example, I found myself procrastinating for two whole weeks recently when it came to implementing a particularly difficult feature. This experience should be familiar to many of us — just ask any end-of-term college student. After 30 minutes of rather painful meditation (at the prompting of a rather unimpressed friend), I realised I was scared of starting because starting meant possible failure. It turned out this fear had sat below the level of conscious thought for weeks.