stress

"In making fine wine, what is ideal is not a perfect environment but, rather, something less than consummate... All of the world's great vineyards are in climates that are in some way marginal. Assuming that the stress (lack of sun, water, and/ or nutrients) is not so severe that the vines shut down, go into shock, or die, an endurable amount of adversity forces grapevines to struggle and adapt. When healthy vines work to grow and the plants are forced to concentrate their sugars in a limited number of grape clusters, the result is grapes and wine of greater character and concentration."

--Karen MacNeil
  from The Wine Bible

I'm more of beer guy than a wine guy (as is evident from my 9-year-old's school uniform below), but I found the illustration above to be a great metaphor for the value of stress in life.

(perhaps I'm drinking too much)