You make a good point, Lori, about dehydration altering one's ability to think and make good decisions. Hypothermia is notorious for this, too. If you allow yourself to get to the point where your mind is malfunctioning, then no amount of survival training will do you a bit of good.

Sometimes, sadly, experienced and highly trained individuals become overly confident of their ability and forget some of the most basic truths about how not to put themselves into a survival situation. In my opinion, easily AVOIDABLE situations account for a hundred SAR events for every one where the person is fully prepared, alert to dangers and proceeds with caution, yet everything goes to heck in spite of that. Such rare events seems to be more akin to what the original poster wants to discuss.

Sometimes the best survival skill is knowing when to stop, reconsider, change plans and bail out.