Walk the Line
Did you hear about the pilot who always flew on the edge of the envelope? His pals called him Stamp.
All activities have a line where crossing it means added risk.
There are three ways to know if you are crossing the line.
Experience, knowledge and crew.
If you have frightened yourself and through the miracle of non-event feedback, nothing happened - you have crossed the line. This experience is used by your brain to warn you. Your stomach gives you an uneasy feeling or butterflies. As in "Uh oh, I have been here before and I didn't like it."
Understand that others have gone before you and recorded their experiences through stories, articles, standard operating procedures, protocols or accident reports. Use this knowledge to understand where the line is. As in "I remember reading about Doofus doing this and it turned out badly."
The crew can assist in recognizing the line by using the two previous methods, experience and knowledge. A simple acknowledgement of the line is usually enough. It can also be the starting point for a discussion on the wisdom of crossing it - much the same as a rumble strip on the side of the road makes the driver aware of the impending ditch.
Stomach as Brain - http://www.nytimes.com/2005/08/23/health/23gut.html?pagewanted=all
In Search of the Perfect Crew