This was a devastating loss for a relatively young, and sometimes over-boastful man. He clearly showed his anguish, by the emotional displays (verge of tears, pounding the ground, slumped posture), and suffered the humiliation of having to eat his boastful words in public.
Truly, I wouldn't wish that on anyone.
Others have noted that Cam Newton was a Fall Waiting to Happen.
However, if he is guided by older and wiser mentors, this could be the opportunity for him to have, in the future, a career comeback.
Failure can be a harsh teacher. The worst part of failure is that many do NOT learn from it - they blame others, brush off the lessons with a disrespectful "tchh" (that sound you make when you suck your tongue against the roof of your mouth), and fail to learn life's most important lessons.
In the aftermath of the Iowa caucuses, Trump is at the same waystation.
He COULD learn from his mistakes.
But, given his response so far, it's not looking likely.