I think someone can teach another to be mentally tougher!

The military, especially elite forces, apply training techniques that make their guys mentally tougher. I admit that to get to that level, there is a degree of criteria of mental toughness needed as a prerequisite, but I would argue that they weren't that mentally tough at age 10 or 15. They had to develop it.

Some of the techniques that they use:

A more grounded or close-to-home example might be running with a friend. Helping that friend, who is exhausted, to make a goal a bit further (just get to the mailbox) and then to extend that goal (now to the end of the block) and so on--that is helping them learn to chunk a difficult task into tasks that seem more manageable. Getting them to recognize that voice inside their head that says that they can't, and then helping them do it anyway--that shows them the difference between self-talk and actual ability.

I would be interested to know @brandonsbytes's thoughts on this. I think he's done some pretty intense training that required him to take his mind/body to the next level.