In this book, author Russ Harris reveals that everyone cannot be happy all the time. Loneliness, depression, and disappointments are the driving factors in human life.
The author signifies that if people are not happy then they are not defective. It's normal that everyone cannot be happy all the time.
Give some space to negative thoughts and feel them. It gradually fades away. It is better than controlling negative thoughts as it leads to loneliness.
He tells that negative thought are not bad instead it signifies that one is more conscious about survival.
Finally, the Author tells us to follow ACT (Acceptance and Commitment Therapy) to control our emotions.