Why this matters
The knife, food, board, and guiding hand work as one system. If any part slides, wobbles, or leaves fingertips exposed, the motion is no longer controlled. Even pieces also cook at a similar rate, so safe knife work improves texture as well as appearance. Work below your maximum speed; smooth repetitions build useful pace naturally.
How to do it
Use the length of the sharp blade: move it forward or backward as it travels down. This slicing motion lets the edge do the work and crushes herbs and soft vegetables less.
What to look, hear, or feel for
A tomato skin should part cleanly and herbs should look cut, not bruised into wet dark streaks. The blade should never slam loudly into the board.
When something goes wrong
If the knife will not slice a ripe tomato or onion skin, sharpen it rather than forcing it. A dull knife demands pressure and is harder to control when it finally slips.
Try it in a real meal
Practice with one sturdy vegetable at a time, without a hot pan waiting, and stop whenever the setup feels unstable.