More than three decades of work with tennis players has helped me understand that the real power broker, in terms of on-court performance and achievement, is your inner voice. The voice that can be brutal or supportive, discouraging or inspiring, childish or mature, is, in fact, the architect of your reality and provides the meaning and context for every experience you have.

Some players possess a voice that amounts to nothing short of an internal terrorist, full of relentless criticism, self-loathing and personal attacks. A dysfunctional voice—one that shouts, “I hate my backhand!” or “You’re so stupid!”—compromises performance in the long run. Others learn to navigate the inevitable storms of play with a positive and constructive inner voice.

How do you find the right voice? Start with the ratio of positive to negative messages you send yourself. Researchers studying athletes have discovered that a negative voice is more powerful than a positive one. What this means is that for every negative message you send, several positive messages will be required to undo the damage. I’ve asked many tennis players to take notes on their thoughts in between games; many come back to me with highly negative ratios, ranging from 1 positive to 2 negatives all the way to 1 positive to 10 negatives. As the ratio of positive to negative improves, the player’s performance gets better, too.

This is easier said than done, but here are five steps that can help you train your inner voice to speak positively:

  1. Pay attention to the tone and content of your inner voice during practice and competition. Estimate your ratio of positive to negative thoughts in each.
  1. Make a list of the major things that cause your inner voice to turn negative, such as bad line calls, unforced errors, double faults, playing pushers and choking.
  1. Assess each situation where your private voice turns negative and write down a new, constructive script that you can use the next time a similar situation arises. Try to summon your wisest, most intelligent voice in your writing. A good reference point is what you would say to a friend or teammate to help him or her perform at the highest level. Develop your script, read it often and make a vow to follow it.
  1. Hold yourself accountable for the messages sent by your inner voice. After every match, reflect on the extent to which your voice stayed “on message” and estimate the positive-to-negative ratio you achieved. This is a great way to measure your performance.
  1. Rewrite your script from scratch whenever you fail to follow it. Every time you rewrite your script, you increase the probability that you’ll follow it in the future. The simple act of writing it down reinforces positive thoughts.

Every message sent by your inner voice is an energy impulse that can change how your brain processes incoming and outgoing data. The brain functions much like a word-sensitive computer. Different words have different impacts. If you have a dysfunctional inner voice, you’re fighting two battles, one with your opponent and the other with yourself. It’s much better to enlist your voice as a silent partner rather than an enemy.

Jim Loehr, Ed.D., is the chairman, CEO and co-founder of the Human Performance Institute in Orlando, Fla.