Once upon a time, before I had kids, I was a professional martial arts instructor. I taught one style and, at various times, cross-trained in other styles in order to round out my skill set and my understanding of the different ways one human being can hit another. Every month or so, I'd get a new student who'd come in with his eyes blazing and his heart full of thunder. Guys like this wanted to learn everything, right away: grappling, wrestling, punching, kicking, blocking, sticks, blades, thro