The most common mistake I see, both before I became an instructor and now, is flinching.
People see a rock or a wave and instinctively pull away. They stop paddling or rowing at exactly the moment they should be working hardest: digging in, bracing, high-siding, leaning toward the feature, or making that last-second move to line up.
Flinching usually turns you sideways. Broadside on a rock, and you can pin or wrap a raft or cataraft. Hit a wave sideways in any boat, and you're far more likely to flip. Square up to the feature ("tee up") and keep your power, and your odds get a lot better. Hit a rock with the bow or stern and you can often pivot off it instead of pinning. None of this is a guarantee, but it stacks the odds in your favor. Even when you mess up, you mess up less and fail forward into a better position.
The instinct to flinch is natural. The goal is to attack whitewater instead of reacting to it.
The same goes for panicking after a swim. Fight-or-flight kicks in, and many people freeze or get confused. The answer is training, because we don't rise to the occasion. We fall to our level of training.
