Why does evil enter one’s life?

The following is an excerpt from a samvaad (dialogue) session with Acharya Prashant.

The Two Hermits
Upon a lonely mountain, there lived two hermits who worshipped God and loved one another. Now, these two hermits had one earthen bowl and this was their only possession. One day, an evil spirit entered into the heart of the older hermit and he came to the younger and said, “It is long that we have lived together. The time has come for us to part. Let us divide our possessions.”

Then the younger hermit was saddened and he said, “It grieves me brother, that you should leave me. But if you need so, so be it”, and he brought the earthen bowl and gave it to him saying, “We cannot divide it, brother, let it be thine.” Then the older hermit said, “Charity I will not accept. I will take nothing but my own. It must be divided”.

Then the younger one said, “If the bowl was broken, of what use would it be to thee or to me? If it be thy pleasure, let us rather cast a lot”. But the older hermit said again, “I will have but justice and mine own and I will not trust justice and mine own to vain chance. The bowl must be divided”.

Then the younger hermit could reason no further and he said, “If it indeed be thy will, and if even so thou would have it, let us now break the bowl”. But the face of the older hermit grew exceedingly dark and he cried, “O you cursed coward, you would not fight”.

~ Khalil Gibran