Mistake! What Mistake?

Dry-cleaning, according to some historical records, was invented when a man accidentally spill some paraffin onto a dirty table-cloth. He was said to have noticed that the part of the table-cloth the paraffin had soaked was clean. Certainly the man could not have been the first person to spill paraffin on a table-cloth. But he was certainly the first to notice the good thing that came out of spilling paraffin on a table-cloth. What does this teach you about the way you think of your mistakes, errors or accidents?