Triathlon training is coming along well enough. The tri I selected is a short race. I'm reasonably confident I could finish the race today if there was some sort of emergency need for triathletes. It would be difficult, but I think I could do it.
Mostly, I'm worried about the unknowns. Endurance sports are a skill that you learn. I know how to do a marathon - where to pin my race number, what to eat, how to manage my pace in the pack of runners. Triathlons are tour through the unknown. How do the transitions work? Are there scary critters in the water? How deep is it? Are there eels? I've decided that eels are a real possibility. And of course, there's the bike riding. Road cycling has not been a friend to me. What if I make a huge fool of myself and everyone laughs at me?
At least I know I'll be physically strong. I've been swimming pool (no eels there!), spinning on the stationary bike and running. In my heart, I know training in the gym has none of the mental stresses of ocean swimming and road biking. It's sort of like sky diving. You can practice all day on the ground, but that doesn't mean you'll be able make yourself take that leap.