About ten years ago, my family made the same mistake thousands of others make every year—we took our young kids to Disney World in the middle of the summer.

Our daughter was still little enough that she couldn't walk very far on her own, so she spent most of the day bouncing between her stroller and my shoulders. Between the relentless Florida sun, the heat radiating off the pavement, and miles of walking, I eventually hit my limit. I remember getting to the point where I could barely see through the sweat running into my eyes.