A newly minted doctor. was practising his patter at a London hospital. He was about to give an injection (shot) to a somewhat gruff, older American man. The doctor warned the patient that, "it was just a little prick with a needle". The patient's reply, "yes I know you are, now get on with it".
What on earth does this have to do with cooking you might ask?
We were simmering potatoes for potato salad the other day. The potatoes were the small waxy kind - the kind that you want to keep their shape. When checking for doneness with a fork, it seemed like they had a long way to go. However when using the tip of a knife, it was clear that they were already cooked. I suppose I could attempt to remember the feeling of the amount of resistance that I felt with the fork, but it was so little different from the resistance I felt when piercing a raw potato. Now maybe my forks are especially blunt. Regardless, I always test with a knife now because I know that is reliable.