St Laurence Justinian says, that nobody knows well what humility is, but he who has received this gift from God; that it is of itself very difficult to be known, and that there is nothing in which man deceives himself so much as in knowing what true humility is.  ‘You think,’ he says, ‘that it consists in saying you are a sinner and a miserable creature.  If it consisted in that, nothing in the world would be easier; we should all be humble, for we all speak in that manner, and God grant we believe what we say and that our words are not just a mere matter of form….by no means; there may still lurk a great deal of pride at bottom.  It may easily happen, that by adopting this mode you wish to distinguish yourself from others, and to pass for a better and more humble man than they, and so all may be but a sort of refined pride. 

–St Alphonsus Rodriguez, ‘On Christian Perfection’