I think we don't remember because it's much, much more fun not to.
My sons both play video games. When the games are new, they are challenged, and play for longer periods of time. They look forward to playing, and it's usually the first thing they want to do when they get up. They talk about strategy, and show new levels to each other. They might even read strategy guides or go online to find things out.
At the new levels, before they've figured things out, they get very frustrated sometimes! Because they keep dying and have to start the level over. But they want the challenge, they want to play.
After they've played the game a few times and beaten it, they might bring it out every now and then. They'll play, but it's not with the same enthusiasm they once had. They know all the tricks and pitfalls, so they beat it with ease in a shorter amount of time. They may play with a friend who hasn't played before, but after a while, the game sits in the game cabinet, and rarely gets pulled out at all.
Even though parts of the game were challenging and frustrating when they were learning them, they got joy from the challenge -- they were having FUN, even in the challenging times.
If we remembered what we learned before, how challenging would our lives be now? Would it be as fun? As exciting?
It's fun to sit back and watch this avatar named Caren get all frustrated about stuff she doesn't know - or doesn't remember she knows. Wheeee! What a ride.
And I just lost the Game
. Darn it.