Teachers are usually pretty good judges of their students' potential. Every once in a while though, one student will come along that either becomes so successful or fails so hard later in life that the teacher can't help but wonder what happened.
Not to sound too cliche but... it is about how you get back up after you're knocked down. No Phoenix becomes a Phoenix if it can't rise from the ashes. That is where all the glory lies. How do we know what we're made of if we're never tested? Though life can through a little extra we could skip once and awhile.