Subtitled Why Being Your Whole Self–Not Just Your “Good” Self–Drives Success and Fulfillment and written by Todd Kashdan and Robert Biswas-Diener, The Upside of Your Dark Side is different from much of the other stuff out there lately. From the official book description:

…(T)wo pioneering researchers in the field of psychology show that while mindfulness, kindness, and positivity can take us far, they cannot take us all the way. Sometimes, they can even hold us back…
The key lies in what the authors call ’emotional, social, and mental agility,’ the ability to access our full range of emotions and behavior—not just the ‘good’ ones—in order to respond most effectively to whatever situation we might encounter.

An excerpt provided by New York Magazine makes an important distinction about so-called “negative emotions” and how most people perceive them.

…(E)xpressing frustration, or even too much sadness, is anathema to most folks. It’s as if we expect ourselves to be computers, whose inner processes are largely hidden and divorced from what appears on the screen. This attitude exists in varying degrees across cultures; it’s part of the idea that it’s easier to live in a society where people are smiling than it is to coexist with people who are shouting.
But it misses the point that emotional expressions exist for a reason. Emotional expressions are an important way in which we communicate with others. A furrowed brow or frown warns people off when you aren’t in the mood (and sometimes you’re not in the mood). A gasp of fear has a contagious effect such that bystanders also feel a jolt of adrenaline and look around nervously. Expressing feelings, including negative ones, is a big part of the human emotional experience.

The authors’ take on mindfulness is that yes, it’s certainly beneficial at times—but so is mindlessness, in fact. (And so is a middle ground between the two.) Creative insight can occur in a spaced-out kind of place.

Both authors of the book write ongoing blogs at Psychology Today. A cogent argument for the role of psychological flexibility is made by Kashdan in “A Secret Weapon in Preventing Anxiety and Depression.” An excerpt:

What do you think happens when you attempt to remove yourself from uncomfortable situations? Your mind, body, and spirit start to atrophy.
Read the groundbreaking research by Dr. Steven Hayes, Kelly Wilson, and others on psychological flexibility, and you will discover one important fact: the cultural message that ‘you should feel good and try not to feel bad’ is among one of the most toxic processes known to psychology.
When we attempt to divorce ourselves from pain, we end up feeling nothing pleasurable or meaningful at all…

Biswas-Diener singles out anger in one of his posts, specifically regarding the differences between men and women.

Here’s the bottom line: for whatever reason–biology, social roles, socialization–women are penalized for expressing anger despite its benefits and naturalness. It is yet another example of a gender inequality that has real world consequences (imagine, for example, women being viewed as hostile in the workplace for showing the same emotional backbone as their male counterparts). Opponents of angry women should bear in mind that anger is part of our natural psychological architecture and discouraging women from expressing it is like suggesting that they try to prevent their eyes from adjusting to changes in light.