The self, or perhaps the imaginary self, is infinitely subtle and traps itself by linguisitic means. Whereas truth is fluid and open, falseness is static and every such static inner position produces as a matter of course a self-justifying and self-perpetuating philosophy, however unpleasant that inner position may be - for example, the crass egotism and attendant arrogance that Nietzsche succumbed to persuading himself was the highest intellectual truth. Though naturally unlike the more rarefied case of Nietzsche these 'philosophies' of self tend to be more implicit than actually formulated.
So on the one hand from outside this all very crude and even humorous - the most limited and unhappy state clinging to itself as truth - but still, particularly of course from within, the activities of this self-deluding 'self' are endlessly subtle - a game of illusions where the illusionist is also somehow the rapt audience. These activities, where the self perhaps actually seeks to persuade itself of the truth of its weakness, are far from isolationist, that is man inhabits a world beyond himself and so for example a comparatively refined person, surrendering willingly to pessimism, has the writings of people like Kafka in his self-justifying arsenal, or perhaps keeps himself topped up in his negative inner state with books on the Holocaust - one of the greatest of boons to this willing inner weakness where the self in its activities, bearing all the apparent hallmarks of virtue, simultaneously congratulates itself on its 'unflinching realism' or 'honesty in the face of reality - whereas in truth it is keeping itself mired in its own mud.
So all in all one has to be very careful with oneself and one's subtleties.