In the fall of 2009, at the age of 55, author David A. Stone reached the conclusion that anxiety, worry and self-doubt were useless mental states. They felt awful, never improved the situation, depleted his health and were roadblocks to achievement. So he decided to remove them from his life. The list of things about which we worry is long and includes illness, financial ruin, loneliness and the opinions of others, as just a few of...