Being Mentally Tough is not difficult, but it does take discipline and desire.

PGC wrote this great blog post about mentally tough athletes...

PGC- Are you mentally tough?

and in it they give 5 characteristics of mentally tough players.  For those desiring to becoming mentally tough, you will, like your jump shot, not be perfect right away.  This too is a process that takes time and repetition.

Jay Bilas also wrote a great book on the subject called Toughness where he gives tips on how to be your best, toughest self on and off the court.  

This doesn't necessarily mean you are the strongest.  Give both a look and see what your think!