I went to Session 2 last year. There isn't that much on the scale of running that will break you. There is the CFA 1 mile, PFT 1.5 mile, Sea Trials were exhausting but that was expected, and then the last day we did a 5K. The Cadre are there to give you a realistic view of the school, but they also are there to evaluate you and give recommendations for your application.
Don't be cocky and think you are the best thing to walk off the bus. Help out your squadmates as you are to be a leader not a solo member and be humble if you are obviously acing the scored events. My Cadre member told me when he wrote my eval that he thought given I had been at WP the week before I would have been intolerable, but because of my quieter lead by example attitude I was one of his favorite candidates.
Also keep in touch with the people you meet there, my Cadre was very helpful in my ROTC application and I still talk to him on Facebook every other week or so.
