If you take one rivet out of an airplane, it will be all right, it'll keep flying. You take another rivet out of the airplane and it still flies. So what the heck, let's take more rivets out of the airplane, and sooner or later, the airplane drops from the sky.
I wanted to further my education, so I went on to get a Ph.D. in electrical engineering and came back and served about ten years in the Canadian Navy as what we call a combat systems engineer.