jjju.g.k.-IMO everything in ones life plays a factor in developing toughness...

Upbringing etc plays a big factor. Actually more accuratly would probbaly be ones interpretation/perspective on thier surroundings and enviroment but essentially yes. I believe it makes a big differance (supporting that thoughness is learned)

Too much stress will lead to weakness.
Too little stress leads to weakness.
Balance

If Mummy and Daddy gave you everything you ever asked for and you were born with a silver spoon you will likely not be 'tough'.

But someone who is terribly abused there whole life will likely not not be tough either (though they might act it).

Thats why, especially the more I learn about how the body and ego etc works, I believe that the foundation needs to be addressed if serious about getting tough.

If one doesn't deal with past issues then they will always effect ones mental/emotional (and physical IMO). To get tough is a mental/emotional thing.

In my experience and with fighters I have talked to I have heard stories of times when they weren't 'tough' and how they over came it and became 'tougher'. Also I have seen toughness deteriorate. I have experienced moments where I was not tough and I think have have become tougher since...