How wonderfully true that is (all of it) but this statement in particular rings so very true for me right now.
We've had several spawns over the past few years and of course could not resist trying our hand at growing a few out just to see what would happen. The first one happened only about a month after we got our very first Koi and you could have fit all we knew about Koi in a thimble with plenty of room to spare

. We gave hundreds away but kept a dozen or so we thought were "pretty"

. The ones we had the highest hopes for almost all went completely to crap within the first year, and most of the others followed suit the next... but we learned something from it nonetheless.
Fast forward to last year. From that spawn we also kept around 100, gave many away, and kept about 40 to watch go up or down as a test of our progress in seeing fish as either good or bad early on. Obviously we got a lot more junk than anything else, but we intentionally kept the best and the worst to reinforce the education. It has been a very fun experiment to say the least, and I'm happy to say that this time our predictions have been about 90% on the money, which is a complete reversal from the past.
There truly is no substitute for seeing the difference up close and personal...