I have been approached several times asking how I have been able to consistently execute at the 70.3 distance year in and year out. Simple answer is experience.
Just like anything else in this world, everyone becomes better at what they do with the more experience. Racing at any given distance takes some time to perfect or at least approach perfection. When I first started racing short and long course, not everything always went the way I pictured it. Swam great, biked terrible, ran terrible. Swam okay, biked well, ran terrible. Swam great, biked great, ran okay. You name the combination or imagine a race obstacle, and I have experienced it.
Then I started to experiment with specific execution elements at races. What if I alternated water and gatorade at aid stations? Do I bring the HR lower the last 3-5 miles of the bike? What if I ran my first two miles 30 seconds slower than what I wanted to? With each experimentation, i learned about myself—come to find out giving up 15 seconds up per mile for the first two miles actually saved me minutes over the course of 13.1 miles! Keeping my HR lower the opening miles enabled me to maintain control over it throughout the rest of the race. If I was feeling good I would hit the gas a bit and pick up the pace knowing that if I got my HR too high (I had a number always in mind before the race), I would back off.
The more and more you race, the more likely you will know what works and doesn’t work for you. Not everyone can race their first 1-2 races and have it go their way. Practice makes perfect. Whether you choose several smaller less important races to experiment on or one major one is your choice, but racing often certainly gives you more opportunities to perfect your craft.