When you're dehydrated, your ability to function efficiently degrades rapidly. Then you make mistakes. We should all drink 3 to 5 quarts of water each day when we are outdoors. A lot of hunters don't even carry water, much less drink that much. It's sheer foolishness.
Panic is harder to deal with.
The first thing to do is sit down. When you're on your feet, you're going to move. Have a drink of water. That way you move from being fat, dumb, and happy to a crisis situation to a coping situation, where you get a grip on yourself and on what needs to be done. Panic is a great contributor to the number of deaths that occur in the outdoors.