Just consider the relative hardness of your flesh versus the pit. And the fact that while you intend to hit the pit straight on, imbedding the knife, if it slips sideways, by the time it hits your skin it’s going to be moving in a slicing motion, which obviously makes penetration of skin and tendons easier. What’s so difficult about laying it on the cutting board? You’re still allowed to hold the end of it for stability, just don’t put your palm behind it.