What really happens when people try to communicate with one another? Specifically, when one person gets up in front of lots of other people and tries to inspire, inform, motivate, teach, change, or lead them?

The first thing that happens is something that you may never have thought about before. The audience starts an unconscious dialog with the speaker, attempting to decode the speaker’s intent. That audience asks itself questions like, is this person a friend or a foe? Do I like or dislike this person? Can I control this person or will this person control me?

Note that this set of queries begins before the speaker starts to speak, so the questions and answers are not about what the speaker says, but rather about the speaker’s visual appearance, posture, way of walking on stage, and a host of other ways in which we can make preliminary impressions – not to mention that audience’s unconscious prejudices, preconceptions, and attitudes.

At this point, the speaker’s past history becomes important because it in large part determines the habitual postures and gestures of his or her body. These have developed over time and represent characteristic ways the speaker responds to the world. They are representative of how that speaker thinks and feels about both good and bad events, stress and joy, opportunities and disasters.

In short, they’re a record of all the accumulated reactions, decisions, fears, and joys – the memories that make up that speaker’s life.

In a very real sense, personal history is written in the body and its literal, physical attitude toward the world. Are you defiant, or do you stand like a victim? Do you dominate the space or take up as little as possible? Are you a leader or always second in command? Do you effortlessly lead a team to get things done, or do you spend huge amounts of time keeping score of all the little ups and downs you encounter along the way, like a spider weaving memories into her web? All of this shows up in your body, especially as it ages.

That presentation to the world becomes more and more unmistakably you, but it also, naturally enough, comes to limit the possibilities as time goes on.

That’s potentially damaging enough. But when you reflect that most of those attitudes, intents, emotions, and desires that come to shape your body’s typical response to the world are unconscious and shaped by your unconscious memories, then you start to see why it’s so important that you understand what’s going on.

And then you start to deliver your speech. What happens next? Ask yourself, in moments of high stress, like a speech, does your body do what you want it to, or does it betray you?

Your unconscious mind may disable you by sending messages of abject terror shooting through your limbic system, causing embarrassing physical symptoms that become impossible to ignore. Or your unconscious mind may make a mess of things by going blank at a key moment, causing you to fail to wow the crowd when the chance comes.

The bottom line is that if you’re not working on your brain to send positive signals through it, you’re doing less than half the job necessary for success. And that perhaps is why most conscious efforts to control nerves so ineffectual.

The dialogue you currently have with your unconscious mind is mostly unmanaged and is a collection of old thoughts, both conscious and unconscious, (mostly unconscious) fears, compulsive ideas, traumas more or less healed, and on and on. Things your parents told you in moments of fatigue and pique, things that you’ve forgotten, shape your thinking along with lessons your body has learned about all the stimuli it has received since the womb. Things you’ve heard, stupid jokes your friends told you when you were eight, movies you’ve seen, books you’ve read, and so on, all jumble together in your unconscious mind, random data that it has assembled from everything that it has seen, heard, smelled, tasted, and felt.

The unconscious brain apparently never forgets. Everything it has experienced is set somewhere in the 100 billion or so cells that make up our vast internal universe. But the way the mind works is that things that are repeated are strengthened, making stronger and more numerous synapses, so that the memory becomes more and more important to our overall patterns of thinking. We attach emotions to events to create memories. The more intense and more frequent an event is—as it strikes us—the more it looms large in our mental attic.

So, for example, if your brain links together the experience of choosing up sides in sports in grade school with your popularity in later years, the social dynamics of your relationships with your colleagues at work, and your divorce, you may have a significant and largely unconscious set of beliefs about your ability to manage a team that kick into place when you try to talk to that team. You may find yourself self-sabotaging without knowing why.

Thanks to the usual unavailability of the unconscious sources of most of our attitudes and beliefs, we may have very strongly held feelings that hold us back without knowing the reason. If we knew the reason, we might be surprised or even appalled.

The reality is that your conscious mind is beset by essentially random directives from your unconscious mind, some of which help you succeed in your larger purposes in life and most of which don’t.

But that’s also an opportunity. Because you can start a positive conversation with that unconscious mind, telling it what you want it to believe and to do, so that in moments of stress you are fully supported and show up as your best self. It’s what Olympic athletes do when they develop mental movies of themselves running through their routines or races with perfect aplomb and great success. That successful movie – if you run it often enough – crowds out the unsuccessful ones you may have accumulated.

As a speaker you can create and use similar mental movies of yourself giving a speech with success and to a standing ovation in order to help you succeed.

If you don’t, you’re leaving your performance, at least in part, to chance.

(This post is based in part on my book Power Cues, published by Harvard in 2014. )