I think I agree with your definition of Mental Toughness oldranger; after I've advocated a common position in this discussion, I'm reconsidering its value. Let me toss a strawman out there and see how it holds.

I don't think we can predict when any of us will run out of mental toughness (really, resilliency). Even those who get back up again after getting figuratively knocked down (mentally or physically) have breaking points. The reaching of those braking points can be unexpected, and excacerbated by poor conditions (lack of food and sleep, bad weather, etc).

So while going hiking with the "mentally fragile" (as an antithesis to the thesis of the "mentally tough" or "mentally resiliant") might not be desireable, I don't know if any of us can predict when we'll crumble. Even those of us who've walked up to the edge, leaned over to have a look, and come back from it as "mentally tough" people.

Some really suprising people survive and succeed in the face of incredible odds. Leadership is my part and parcel of my profession, and I don't think I know who the "mentally fragile" are, and don't think I could pick them out like ppine suggests before hiking with them. Diamonds are only found after time and incredible pressure, but even diamonds crack after one hit too many - past performance is no garuntee of future success. So while we can define resilliency, I don't think we can predict it with a great degree of certainty.

What do you think?