i remember than in eastern orthodoxy, they have this theological concept called "prelest" or "plani", which meant "spiritual deception". since the eastern orthodox rite is big on mysticism and monasticism, they had a lot of cases whereby monks, or even lay people would be deluded in their spiritual path by satan. they would see or hear visions, claiming to be angels or saints, or god himself. then the visions would make them believe that they've "made it", so to speak, in their spiritual path, leading them to believe that they're better than everyone else, that they're sinless, that they're for sure going to heaven, or that they're saints, etc. anyway the most important rule in eastern orthodox mysticism is: to be humble, because pride is the way that leads you to spiritual deception. st Anthony, which is sort of "the guy" when talking about overcoming demonic deception, relates a story where he saw demons scattered throughout the earth. he then asked, "lord, who can escape these snares" or something like that. he then heard a voice saying "humility".
http://en.wikipedia.org/wiki/Prelestthen of course, when reading about this concept, I then remembered about what was written about Muhammad in the muslim sources. stuff like him saying he's the best of all mankind, that he deserved to be loved more than the believer's own life, the perfect example, him being sinless, etc.