Knowledge is the basis of plans, and experience is often the source of knowledge. I had some relevant experiences to help me prepare for Mooseman:
1. Olympic Triathlon: The swim in an Olympic Tri is something like 75% the distance of the swim in a half iron. What I knews is that not only had I completed the Olympic distance swim, I had ADORED it. The rhythm and solitude of an open water swim is an amazing experience. I knew that not only could I probably do the distance, I could probably enjoy it.
2. North Bay Triathlon: From a swimmer's perspective, I'm a competent swimmer at best. From a triathlon perspective, though, I'm a strong swimmer. So why did this 500m swim destroy me so badly? COLD WATER. I learned that I did not handle cold water in my face well in swims at all. Knowing that Mooseman could be even colder motivated me to spend both money on a good body length wetsuit, and time mentally preparing myself for the start of the swim.
3. 3 marathons: My goals for the 3 marathons were: finish, improve my time, and try for 4 hours. My results were finish, improved my time, and went 4:06. Sounds good, right? Still, all 3 featured some kind of a nutrition failure - cramping on the first two, and dehydration and hyperventilation on the third. All three races, I hit a point where I obeyed my stomach and stopped taking on nutrition. In a half iron, which is much longer than a 4.5 hour marathon, this would simply not be permissible.
The most important part of my plan involved nutrition. I had detailed plans for what I would eat/drink at T1, T2, and how much I would eat/drink on the bike and run. I brought extra foods with me, including soda crackers, trying to anticipate potential dietary problems. I did extra reading on race nutrition. I reviewed the race literature carefully, noting that their promised aid stations were amazing, and adapting my plan to incorporate them.
I also gave careful mental preparation to the subject of pacing. Going out too fast in a half or full marathon can ruin any chance of a PB. Going out too fast in a half iron must therefore be even more dangerous. I told myself that I simply would now have an idea how my race was going to go until I was off the bike. That meant that I was going to have to conserve my energy, and limit my speed, for hours.
There was a lot of contemplative mental preparation that went into the pre-race buildup. I confronted my fears about the cold water, reminding myself that once I had gotten past my panic in North Bay, the temperature had gotten easier to tolerate. I charted nutrition aggressively, and thought through what might happen if my stomach revolted at some point. I visualized myself walking long parts of the half marathon, but still being happy.
I tried to address every real fear and concern I had, knowing that the race day might be even stranger and more stressful that I could foresee.