Imagine the scene: Your company is about to pitch a group of investors who can make or break your business. You know there is one individual you can rely on to seal the deal because of his track record. You call on him to once again deliver a convincing and powerful . He's clearly nervous as he should be: This is an important pitch.

You utter the simple words that have been the curse of many a professional: “Don’t mess up, whatever you do.” These words ring and echo in the presenter’s mind when walking into the room of clients. “Don’t mess up, whatever you do,” he says to himself.

He opens his mouth and delivers a babbled and stumbling introduction, setting himself up for a nervous and jerky 15-minute presentation. You emerge from the pitch bemused, aiming disappointed looks toward the presenter. “What happened?” you wonder.

Related: Petrified of Public Speaking? Keep These Tips and Your Audience's Fears in Mind

Don’t say don’t.

It is quite common to see failure snatched from the jaws of victory because at the crucial moment, a person's focus turns to potential failure because of simple “don’t” statements: Don’t mess up. Don’t fail. Don’t worry.

Prior to a big presentation many professionals say to themselves, “Don’t stutter” or “Don’t worry about the audience.” But under pressure, the brain doesn’t really understand the word “don’t.” Oddly, “don’t” can turn into “do” when someone is stressed.

But telling people not to do something can increase the likelihood of their doing it. To make matters worse, these ironic processes are more likely to occur when people are anxious, which is bad news for pretty much everyone who experiences some degree of anxiety before an important event.

This has to do with the way the mind works under pressure. When people are anxious and their mental resources are used up by worry and concern, their ability to focus on aspects that will help them perform well is impaired.  

So saying, “don’t mess up” to someone who is anxious or facing a pressured situation can prompt her mind to focus on failure rather than success.

Related: 5 Steps to Conquering Public-Speaking Anxiety

Focus on positive instructions.

In our new book What Business Can Learn From Sport Psychology, we flag one of the best ways to combat ironic processes: making sure that a person’s focus is fully fixed -- like a laser -- on the things she wants to do in that performance. Have her focus only on the things she needs to do to perform well.

If producing a fluent and proficient opening statement is vital, help her focus on only doing that -- not on the consequences for failing to do so. Give her some key phrases to focus on. Say, for example, “This pitch is important, but focus on a nice fluent and enthusiastic opening statement and then settle into your delivery.” This is instructional, focused on success.

People are more successful at avoiding negative thoughts if they're given an alternative to focus on. So when unwanted thoughts of failure come to mind (which they surely will), she can replace them with images and thoughts of what she needs to do to succeed.

Related: 8 Ways to Drive Entrepreneurial Stress Out From Your Life

Empty the mind of worries.

While it's extremely difficult to completely rid the mind of potential negative consequences, it's possible to help someone shed negative thoughts. Instead of encouraging someone not to worry or to suppress concerns about a performance, help him express these worries and concerns way in advance.

By helping the staffer express the unwanted and negative thoughts, you help him remove the need to suppress them. Have the staffer write his concerns and doubts on paper. Tell him to put down exactly what's on his mind: fears and concerns, possible negative consequences. Then have him silently read this, rip up the paper and throw it away. This is not for your eyes – only he knows what he wrote and the paper is destroyed.

In helping people express but not suppress unwanted thoughts, you remove power from the ironic process.

Related: 4 Motivating TED Talks to Help You Bounce Back From Failure

Be ironic to fight irony.

It would be unwise to let unwanted thoughts run free on the day of a big pitch or even the night before. Instead, give staffers time in the days before that presentation to consider potential failure and even let their mind drift to contemplating past failures.

As people are being given an opportunity to think about past failure in this way, they may realize that the defeat wasn’t as bad as they first thought and that they coped with the setback.

After all, despite a previous failure, they are still there doing what they are do and have probably learned a lot from the experience. Remind them that their heroes and role models probably failed on their way to success (perhaps many times) and survived.

And why not share your failures with your staff? This can help create a culture in which negative thoughts are given time and space to be let out instead of locked inside to fester -- only to appear when least expected moments before a pitch.

Related: How to Deal With the Fear of Being Unqualified