"How about mental fitness? While watching some of the documentary "Summit on the Summit", I recalled how much of a surprise it can be to newbies that a significant portion of the experience is suffering with wet gear, cold hands and toes, fatigue, physical pain, self doubt, fear of failure etc. Good partners (or guides) will help overcome some of these issues but in the end it may come down to confidence in your preparation and mental toughness."
The only way to overcome this is by climbing, preferably in tough conditions, with people you trust.