It's okay to be selfish.
But in a healthy and constructive form of selfishness.
This is what this book by David Siberry is trying to tell you. As you become more aware of yourself and the world, you will find that you need some selfishness. Common in human discourse is to glorify the virtue of self-denial and to denounce every gesture of the self-voice. But the truth is that being a selfish person is the exact opposite of what you think when it comes to caring for others. If you become a healthy selfish person, you will become better able to care for and help others. Your preference for yourself will make you give yourself the care that is most appropriate for you. This, of course, does not mean that you become a person who is indifferent to others around you. What the author means is that you ignore the things that tire you and are unnecessary in the life around you, in order to preserve your right to balance and comfort.
By practicing the right amount of positive selfishness, you will find that you enjoy fewer losses, which will save you from much of the pain that comes with the stress of trying to please others. Furthermore, your priority gives you the opportunity to consult yourself. Before you undertake any action that you are not obligated to do, you will ask yourself whether it causes you comfort or unhappiness, and you will save yourself the trouble of experiencing it with insufficient awareness of its effects.