Kona, allot of peoples dream race and buckets list items to do, but for allot of us, it's either a hit or miss. 
Being in the sport of triathlon now for 15yrs starting at the age of 16, i've definitely gone through the roller coaster of "ups and downs" with the sport of triathlon and not trying to speak for everyone but it usually consists of a lot more 'downs' than 'ups'. 
With age and experience you try and learn from your mistakes and try and counter for the things you can control, i call them the "controllables", everything else it's out of your hands so i try not to think about the "what if's". 
For me my kona experience i did everything right on the "controllables" side of things, it's still and hard one to swallow but what happened for me race day was out of my hands.
A recap of what my race went like... 
The race started, and kona is a little more aggressive than your typical ironman event, everyone's fighting in the swim for that extra inch and no one's taking any prisoners, it's a tough swim as everyone there is quite good, so you're either fighting to stay in the group or your out the back, which no one wants especially me. 
My race was going to plan, got out with the front main group in the swim, as i collected my bike i notice my glasses was knocked off my bike in the mad scramble, was nothing i could do as i had to go with the race, no time to "look in lost out found".
Bike was hot to begin with, (as expected) i positioned myself nicely in the middle of the group making sure i'm not losing contact of the race. 
We (the main group) i  had just got onto Ka'ahumanu highway part of the bike course and the pace seem to have now settled, with the combination of my pre-race sunscreen and the sweat/humidity my arms were very slippery, i hit a bump in the road and went flying over the handlebars.    
I got up as quickly as i could (post 1st crash) and my bike chain was jammed up, so i lost nearly a minute getting back onto the bike, i was really sore riding now when i returned to the race, my entire left side was aching, but i tried to stay positive and hoped that i could possibly get a second wind that might bring me back into the race. 
I was losing time,  i lost any sort of momentum i had from that first crash, i still was trying to think of the positives and maybe just maybe i might have a great marathon as a saving grace. 
Approaching around 150km mark on the bike, for a split second i lost concentration on the bike and accidently road straight into the lava fields.
This was the nail in my coffin, that crash in the lava fields with the sharp hot rock, i just swelled up and to boot got severely burnt too, i couldn't move, my day was now over. 
Again the was a tough day to swallow, but having now some time to look back at it, it's "just life" as they say, and i got to ride a few more downs till hopefully i get back to some of those ever satisfying 'ups" 
Onwards and Upwards