Disclaimer: I'm super new to MT and driving anything with more power than a 2000 Subaru Forester.  
Second day of driving my Box I did 
EXACTLY what this guy did while making a left hand turn (driving hard obviously).  What went wrong?  I think I lost traction when I shifted into second while turning or something?  Came close to wrecking - wound up 180 in wrong direction finally stopped next to the other cars turning left in the opposing target lane..  Super embarrassing too!