I understand your sentiment, but I disagree.
The most important thing?
... a will to survive.
Of course you are right, but I was taking that as a given since those with no will or a weak will to survive will likely not survive no matter what.
A sense of humor is also required if one wants to not only survive but have any quality of life. When things are really not going your way sometimes the only way to see it is to not take it too personal or serious. One of the things city folks seem to comment on the most when they get familiar with country folks is our sense of humor, especially in situations that don't seem to fit with humor.