Public Speaking Fear is All in the Mind

According to the October 25th Newsweek article there is agreement among researchers who study the processes of mind and brain that underlie belief. "As scientists began studying belief in the paranormal, it quickly became clear that belief requires an open mind—one not bound by the evidence of the senses, but in which emotions such as hope and despair can trump that evidence."

The article went on to say that "the brain's sensory regions, including vision, are at the mercy of higher-order systems, such as those that run attention and emotions. If attention is not engaged, images that land on the retina and zip back to the visual cortex never make it to the next stop in the brain, where they would be processed and identified and examined critically."
Neuroimaging studies have shown that there is a "constant back and forth between cognitive and emotional regions of the brain. It can intensify perceptions as when fear sharpens hearing but it can also override the senses."

What does this mean for public speakers? Fear can intensify your perceptions. If your attention is not fully engaged, a serious face in the audience can be perceieved as hostile or the pleasant, receptive expression can be missed all together.
This is why speakers have an "out of body" experience where they don't remember what they said. Focus your attention on your breath, slow down, and be fully present.
In other words, get over yourself. It's not about you, it's about them.