Well, they don't have to be static things like a book. They can
   be living things - but everything outside yourself has the
   potential to fall away and be gone. habits and addictions are a
   good example. (and, in a sense, they are static - you might be
   right about the static - you don't expect your leaning post to
   move on you...) But if you can train your soul to be more and
   more self-sustaining - added to by external things but not
   depending on them for your soul to continue - you will be okay
   no matter what happens to you. I guess you could translate
   "soul" into "peace of mind" and it would still work. What do you
   think? "