I believe that we are in no way responsible for the decisions of others, so just let it go. You can beat yourself up over this forever, or just accept that he made a different decision than what you would have done if you were in his place.

You can make something positive out of this experience by thinking about how you handled things back then and how you might handle a similar situation now. Turn what you feel was bad into something good and great for other players you come across.