The first of the Four Noble Truths that Buddha taught was "Life is suffering." Adversity is part of the package.

The people who the author was privileged to interview have all endured tremendous tragedy in their lives.  However, through the strength of their spirit and through their refusal to sink into the quagmire of depression and despair, they somehow transcend their difficulties.  Instead of cursing their adversity, they view it as a learning curve, a stepping stone to something better.