[Sohcahtoa82]

When you're a kid, so many experiences are new, so the emotional response is higher.

A kid might fall off their bike, get a minor scrape on their knee, and cry because while the pain is pretty minor, it might actually be the greatest pain they've ever experienced in their life.

As an adult, you're probably not experiencing a lot of new things, and the new things you're experiencing are likely variations of things you've already done.

Though uh...I've seen my wife's boobs thousands of times, yet my brain still reacts like it did the first time. >.>