I'm like Terri--only 100% or nothing, and like Terri this was always true when I was a kid as well. I know I didn't dress all the way then the way i would today, but that was only because I didn't have the access. So I'd say I was dressed all the way even then, at least as much I could.
I also don't understand underdressing, but I wish I did! I wish I could satisfy the need a little underdressing, but it just doesn't appeal to me