Pay attention is great advice. And pay attention not only to your own work, but also what is happening around you in the shop (hint: there probably shouldn't be anything else happening around you when you are doing certain tasks).
This isn't knife related, but one of the many strange stories I've come across working in the clinic that begs you to pay attention to what is happening. A number of years ago, I was evaluating a fella for new sockets for his prostheses. He was a double amputee (one above knee, one below knee). While taking his history, I asked how he had lost his legs, and his reply was that he was "run over".
My immediate response was, "you were in a car accident?"
His reply was, "no. It was a 707."
Me: "A 707? Like a jet airplane 707?"
Turns out he was working on the ground crew doing maintenance on a visiting celebrity's jet. He told his super that he was going down to check the main gear, and while he was there, facing briefly away from the landing gear, someone started moving the jet with the pushback tractor/tug. Before he realized what was happening, the gear had rolled up on the ankle of one of his legs, preventing him from escaping. He was able to throw himself to the side, saving his life, but the landing gear proceeded to run over both of his legs.
He told me how he watched as his legs "exploded and flattened like you see on a cartoon" as the jet ran over them. His screams brought people immediately, but they were all freaking out by what they were seeing, and he was the only lucid one. He starts yelling instructions to people to take their belts off and tourniquet his legs, call EMS, "stop taxying the **@^ing jet", etc.
Anyway, he got a nice fat settlement for the incident; however, it will never replace his legs. It only takes a second or less, and your life can be completely changed.
Salem, I've done similar things back when I used to hand sand without any supporting structure under the blade. I stabbed myself twice in nearly the same spot within 15 minutes when sanding back and forth (rough sanding work) and going off the tip unable to stop the return stroke before jamming myself into the pointy end of the blade. I definitely clamp things down now and use sanding sticks instead of paper in my fingers and knife in hand.
--nathan