Mantras have become popular with triathletes, but as simple as they are, mantras can be a help or a hindrance.  To get your mantras to be as effective as they can be, there are a few simple ideas that can really help you.  A mantra is a simple, brief phrase that you repeat over and over to help you.  Let's make sure it does.
Some athletes make a distinction between a mantra (a sacred phrase repeated often) and an affirmation (a saying intended to produce a positive mental state).
With the help of many D3 Multisport athletes who completed a survey about mantras and affirmations, I have come to three conclusions aimed at making positive self-talk more useful.

1. Not all mantras and affirmations are created equal.
2. The phrase of the mantra or affirmation must be literally true. 
3. The phrase works best when stated in the affirmative.

Not all mantras are created equal.  There are:

• Mantras about your performance.
• Mantras about your identity.
• Mantras about your capability.

Mantras About Your Performance
“I’m going to win.”  Much has been written about the difference between outcome goals and process goals.  An outcome goal might be: “I’m going to win my age group and qualify for USAT national championships.” A process goal might be: “I will execute all parts of my race plan.”  Processes are largely within your control, while outcomes are not always so.  You can’t control who in your age group shows up on race day, or if you have a flat tire.  You just have to adjust to those things.  

Mantras that are outside of your control do not create harmony in your inner mind.  Mantras and affirmations work with your unconscious mind.  Your unconscious mind has an excellent—no, very excellent—crap detector. And it takes things you say very, very literally.  So, when your mantra is “I will win,” instead of focusing on what you tell it, your unconscious mind starts to detect and evaluate and chatter back: 

“Hey, hey, hey, hey, hold on, wait just a minute sister, you didn’t exactly win this race last year and the same athletes who beat you last year are racing today and you haven’t felt very rested recently and I noticed your power-to-weight ratio hasn’t exactly been soaring since you gained that three pounds and what about that sore left calf and you are one year older but some young and fast athletes have snuck their noses under your age group tent and….”

You get the picture.  Instead of producing a soothing, productive mantra, you have triggered your unconscious to engage its excellent (no, very excellent) crap detector to set up some very uncomfortable internal dialog.  You can use process goals, however, to help your mind focus on what you are doing at that minute, with your unconscious mind in full congruence.  “I’m going to execute my race plan” can become, right at that moment, a mantra about your present performance. 

Here are some examples supplied by D3 Multisport athletes:

• “Come on girl.”
• “Go go go.”
• “You’ve run a mile before.”
• "1,2,3,4,5,6" (while swimming to get a rhythm).
  
• “While running in sync the breathing with my running pacing like inhaling every 5 steps, is not a "spoken' mantra phrase but I use it for rhythm.”
• “Race happy.”
• “Relax.”
• “I will keep my form from start to finish.”
  
• “I will run from person to person.”

Mantras About Your Identity
Some mantras are about the athlete as a human being.  Mantras about identity can be especially strong and durable as they go to core beliefs about self-concept.  Athletes (and people, too) work very hard to maintain their self-concept and do not easily perform otherwise. 
More examples from D3 athletes:

• "The Devil Whispers: You cannot withstand the storm. The warrior replies, I AM the storm."
• "If you survived drug addiction, obesity, and abuse, you can make it through this. You are the storm today, raise hell.”
• “You are extraordinary. You are a badass.”

Mantras About Your Capability
Mantras about what you can do can be very powerful.  They often have context and rationale, which contribute to having them be based in the truth, or at least enough logic for your unconscious mind to go along with them.

D3 athletes again:

• "You've done the work, No expectations. Do the best you can and it will yield great results."
• “You’ve got this. Trust the training. One step at a time.”
• “You’ve got this—you’ve done the work. It’s go time. If it’s meant to be, it’s up to me.” 
• “I have the courage to do this.”

Sometimes the mantra is someone else’s voice and words.  For example:

• I believe in you Dad.
• I am proud of you Dad.
• I know you can do this Dad.

State Your Mantra in the Affirmative
Why affirmative?  One athlete’s mantra is "Don’t get dropped."  Take a second to try that one on for size: repeat it a few times.  

Now try the affirmative version, something like “Hang, hang, hang with that group.”  Or “Keep up, keep strong.” 

Run those, or similar ones of your own choosing, a few times.
Now compare to “Don’t get dropped.”  

Which version is more useful?  For most athletes, the affirmative version is more powerful.  In order to process “Don’t get dropped” your unconscious mind first must construct an internal image of getting dropped, then try to imagine what “don’t get dropped” looks and feels and sounds like, then figure out how not to do that thing that it just imagined, and, well, that’s a lot of processing.  Since your brain already uses 30% of your total glucose budget, having it have to think hard while you are racing hard is a bit of a waste of energy.  Make it easy on your unconscious and state your mantra in the affirmative.

3 Point Checklist for an Effective Mantra
When constructing or selecting your mantra:

1. Notice which type of mantra (performance, identity, capability).
2. Check to see that it is literally true. 
3. State it in the affirmative.

Thanks to all the D3 athletes who helped with this research.  
Practice, enjoy and befriend your mantra.  
Onward (one of my mantras).

Will Murray is Team D3's go-to specialist for mental skills training.  He is a USA Triathlon Certified Coach holding a Practitioner’s certificate and more than 100 hours of advanced training in Neuro-Lingustic Programming.  He works with beginners to Olympians helping them use their heads to do more than just hold their hats!