Transpose that to the fly cast. I've heard, over and over, that a good fly cast is "all in the wrist." And that's complete baloney. You can get away with "wristing" a cast at very short range, but when you want to unfurl a longer cast, you need a large "lever" to power that cast, not a small one. Use only your wrist, and you have no more than six inches of flex and power to make your shot. Make your arm the lever, by maintaining a semi-stiff wrist through the casting stroke, and you also put appropriate energy into that long fly rod, where it belongs.