I.E. You are walking along and you see your girlfriend (or boyfriend) with a member of the opposite sex. Doing something which looks wrong and you immediately go over and hurt the guy (or girl) and then find out that it was just a friend and was something totally different.
If you would have thought to just walk in and have them explain you would have realized the truth. This is very hard to notice because you could be right. The only way to always be right is to use your head not emotions...