I often wonder. I think it has something to do with the combination of discerning insight and experience on one hand, and the ability to follow through on such insight on the other.
Been thinking on this a bit more. Perhaps it is this, after Job's encounter with God:
"My ears had heard of you
but now my eyes have seen you.
Therefore I despise myself
and repent in dust and ashes.”
Job had many blessings, but along with the blessings crept in pride, self-righteousness, hypocrisy. This is normal in spiritual growth. In order for Job to continue to advance, there had to come a time of stripping, weeding out, pruning the branches. This is where the suffering came in. He tried to submit at first, but then as things became more intense, he encountered that part of him which, until that point, refused to submit.
Tremendous pressure was brought to bear through circumstances, physical discomfort, and through the words of his friends. Things got a little sideways, Elihu came in to get it back on track. Finally, Job is brought to the end of himself, to a place where God could do what he intended all along: set Job's feet on new ground, better ground. All is restored and even multiplied.
So what is wisdom? Perhaps realizing our true standing and God's true standing. Submission to suffering, ridicule perhaps, being emptied of everything in order to be filled. Possibly?