It seems good advice has been given, particularly by ELKampMaster. I like his suggestion to try to toughen up your mind through visualizing yourself enduring in the face of difficulties and think that sounds like pretty good advice. You might think about taking your own saddlebags (I have heard that if an outfitter supplies you with saddlebags they may be somewhat decrepit and unserviceable). A rifle scabbard might be a good idea too for the same reason or that your rifle might not fit into their scabbard well. You might also plan to carry a good camera with extra batteries, assuming the camera requires batteries, although this is probably in the "that's obvious" category. Carry good rain gear.