This is my 4th year doing Triathlons. Some people would consider me an experienced triathlete, but believe me I'm still very new.
I do know a thing or two about racing though.
Tomorrow, I'm racing The Trishark classic for the 4th year in a row, and here is what I know. In 4 years of racing, every race has had an obstacle to overcome. It might have been crazy heat, wind, snow, rain, a mechanical issue, or eating the wrong thing, but every race has a story.
And so, going into my 4th race I know better than say "this is the race where everything goes according to plan." Instead I'll be saying "In triathlon, anything can happen. I'll react, roll with it, and keep going. No matter what the race brings, there will be a great party afterwards and I'll be better for the experience."
So, my advice as a "grizzled veteran" to someone doing their first race tomorrow is this. Something unplanned will happen tomorrow, but you'll be prepared. You'll deal with it, and no matter what happens there will be a great party and a new story to tell in the end.