Q: How do you train for a triathlon?
A: You knock off corners.
The closer you get to a race the closer your training should get to the actual event. Three months ago when I signed up for the event I had to start with the basics: just going the distance. So that was my first training block, long bikes, swims, and runs. Don't worry about pace or times, just get in the miles. There is no point trying to go fast if you can't first go the distance.
My second block was the next big obstacle, going hard and fast for long periods. On the bike I attacked big, long hills, and in the pool I focused on pulling hard and refining my technique. This was the period of getting strong, powerful.
Now that I am in my third and final training block I'm putting it all together. Practicing biking after swimming, running after biking. Riding on the trails instead of the roads, swimming in the lake instead of the pool. Trying on wetsuits, practicing nutrition. This law is called the specificity of training, that as you approach the race your workouts mimic it more and more.
Like carving something, you knock off corners. First the big ones, the obvious ones. Once those are gone you move onto the slightly smaller pieces, until finally you are cutting out the tiniest imperfections and the sculpture is complete.