I think you totally right on the 'purity' issue. Cat's thirst for God manifests itself in his desire for purity and the tension that can arise over this is a real test. The temptation to flee from God can become quite overwhelming at such times . . .St John of the Cross talks a great deal about this: the more intensely we become aware of the light of God shining upon us the more intensely we become aware of our inadequacy and our shere spiritual 'ugliness' by comparison. John then goes on to show how this is indeed a purifying fire which does cleanse provided we can stay in the light and not rush away in horror at our own darknesses.
. . .on a slightly different tack:
Being an artist (of sorts) I sometimes wonder if all art isnt an attempt at inner 'cleansing': a sort of 'replacement' (or an inner 'extension') of the old 'sacrifices' of the early Jewish faith. Certainly I am again wrestling bigtime with the dualisn of my 'spiritual' life over and against my 'artistic' one at the moment and the question of longing for the purity of God hovers over everything.
For the Christian artist therefore the vision of the cross can never be far away.