Albie,
My theory, for what it is worth:
The 110% gung-ho, oh-rah, there is nothing better than living in this mud hole with my K-bar types get disappointed when they realize the military career is not full of the stuff they dreamed or expected. This leads to disappointment because the reality of a military career does not live up to their lofty expectations. Some of these types do chill out and their expectations are changed.
Meanwhile, others come in thinking this would be a great experience, I can serve my country and see the world. Their expectations are not as high and therefore they fit in much better with the real military. I believe those that find themselves in the middle, the not so crazy gung ho nor the figured I'd join before they drafted me types, do best in today's military.
Anyway, it's just my theory.
I think I worked hard in flight school - but definitely not as hard as others... I was too busy working on my water-skiing form and basketball game, amongst other things.
BTW... I really wanted to be a pro basketball player but I took my second choice as a military pilot. Not everyone can be like Mike

. I know other pilots that really wanted to be porn stars... they also settled.