1. Be impeccable with your word. You can read this as "don't swear", but it's not about that. It is about the constant and continuing things we say to ourselves that make us feel bad. We don't even know we do this. And it's not about big things, it's about the thousands of small reprimands we give ourselves that hold us back living our life.
2. Don't take anything personally. When someone else says something to you, good or bad, it shows how they feel. What they say is about them, what they think is important, what is relevant for them. It's not about you. This doesn't mean that you can ignore it, but it shines another light on things other people say about you, or about others to you. This applies to "good things" as well. If someone gives you a compliment, it tells something about them. And of course it works as well for the things you say or do - they tell something about you.
3. Don't make assumptions. Don't think you know what other people think, or that you know why they do the things they do.
4. Do your best. You can't always live your life following rules. Do your best, and if you break a rule, bad luck, next time better! That means that you can forgive yourself. And it means that you should not give up after a big fuck up. Or a small fuck up, or many fuck ups. You can start over again at any moment.
The book is much better at explaining. It's about 60 pages, worth the effort.