The most serious vice innate in most men’s souls is one for which everybody forgives himself and so never tries to find a way of escaping.
You can get some idea of this vice from the saying that a man is in the nature of the case ‘his own best friend,’ and that it is perfectly proper for him to have to play this role.
It is truer to say that the cause of each and every crime we commit is precisely this excessive love of ourselves, a love which blinds us to the faults of the beloved and makes us bad judges of goodness and beauty and justice, because we believe we should honour our own ego rather than the truth. Anyone with aspirations to greatness must admire not himself and his own possessions, but acts of justice, not only when they are his own, but especially when they happen to be done by someone else. It’s because of this same vice of selfishness that stupid people are always convinced of their own shrewdness, which is why we think we know everything when we are almost totally ignorant, so that thanks to not leaving to others what we don’t know how to handle, we inevitably come to grief when we try to tackle it ourselves.
For these reasons, then, every man must steer clear of extreme love of himself, and be loyal to his superior instead; and he mustn’t be put off by shame at the thought of abandoning that ‘best friend.’
Plato on Narcissim