The Courage to be Happy by Ichiro Kishimi and Fumitake Koga:

The author team behind worldwide bestseller The Courage To Be Disliked return with the must-have companion volume. In The Courage To Be Happy, Ichiro Kishimi and Fumitake Koga again distil their wisdom into simple yet profound advice to show us how we, too, can use twentieth-century psychological theory to find true happiness.