It’s called The Upside of Your Dark Side: Why Being Your Whole Self—Not Just Your "Good" Self—Drives Success and Fulfillment, and Robert Biswas-Diener describes the basic thesis of their book like this:
In the modern era people are able to achieve comfort better than at any time in history. Unfortunately, comfort addiction is making us psychologically weaker. Today, parents want their kids to be socially accepted and have high self-esteem even as they recognize that in academic subjects like math challenge and frustration are an important factor in success. Similarly, workplaces are increasingly treating happiness like a demand instead of a reward. In The Upside of Your Dark Side two psychologists present the fascinating case that guilt, anger, sadness and other darker aspects of our nature are occasionally beneficial … that to be whole, people need to embrace both their lighter and darker halves and this book offers vital insights into that process.