A Helpful Saying?

I don't know exactly how this came into my head one day. Had I first read it somewhere else, or had I heard it in some song, or was it from a jumble of many different influences now long forgotten? 

I only know I jotted it down in one of my many old notebooks, rather quickly and sloppily, in the margin of a section on teaching Book 1 of Aristotle's Nicomachean Ethics.

It has now been stuck in my memory for over twenty years, and it has sometimes allowed me to walk away, only slightly tattered and torn, from many painful circumstances. 

As I always say, your mileage may vary. It may not speak to you, but it has saved me many a time.

I never lost it to begin with.

It was never mine to begin with.

I never needed it to begin with.