The third answer is the most difficult one to grasp, but it's also the one that can save you. The love you lost, or the love you wished for and never… - Susan Cain

In fact, public speaking anxiety may be primal and quintessentially human, not limited to those of us born with a high-reactive nervous system. One theory, based on the writings of the sociobiologist E.O. Wilson, holds that when our ancestors lived on the savannah, being watched intently meant only one thing: a wild animal was stalking us. And when we think we're about to be eaten, do we stand tall and hold forth confidently? No. We run. In other words, hundreds of thousands of years of evolution urge us to get the hell off the stage, where we can mistake the gaze of the spectators for the glint in a predator's eye.

Probably the most common — and damaging — misunderstanding about personality type is that introverts are antisocial and extroverts are pro-social. But as we've seen, neither formulation is correct; introverts and extroverts are differently social.

Indeed, excessive stimulation seems to impede learning: a recent study found that people learn better after a quiet stroll through the woods than after a noisy walk down a city street. Another study, of 38,000 knowledge workers across different sectors, found that the simple act of being interrupted is one of the biggest barriers to productivity. Even multitasking, that prized feat of modern-day office warriors, turns out to be a myth. Scientists now know that the brain is incapable of paying attention to two things at the same time. What looks like multitasking is really switching back and forth between multiple tasks, which reduces productivity and increases mistakes by up to 50 percent.