In truth, science and experience prove that you will race faster if you maximize the efficiency and effectiveness of your physical training. Your mental discipline will make each training session a success and prove to be the real reason for "breakthrough" workouts. Time spent learning to focus on training goals, overcoming training challenges, and enjoying being a triathlete will allow you perfect your training.
When someone has a poor race, they often say, "I just need to train more." If you catch yourself saying words like this, take a moment to reflect on your physical performance. Was it truly a result of your lack of training, or were you slow in the swim and tired in the transition because you believe that "practice makes perfect" rather than "practicing perfectly makes perfect"? Were you slow or fatigued on the bike because you did not train enough, or did you neglect hill or interval training in order to get "more time on the bike"? And just maybe your slow run time was a result of burnout and not too little training.
To succeed on race day you must train successfully. Each workout must have a time and a focus (endurance, speed, force), and as an athlete you must mentally discipline yourself to physically train with purpose. Remember: quality versus quantity.