Your MENTALITY creates your REALITY. It is Satan's mentality that changed him from an Angel to what he's become today. 
(source)
https://goo.gl/images/hL7C5f
We all have that same proclivity, and since freewill abounds, it is only logical that any creature gifted with it must cleanse it constantly by ridding its mind of anything capable of causing and fostering Spiritual, Emotional, Psychological, and to material extents, Physical, and Financial pollution.
"...the subconscious mind is a fertile garden spot in which weeds will grow in abundance if the seeds of more desirable crops are not sown there." [NAPOLEON HILL