When and How to Talk of One's Self : Page 216
In all three types of talking of one's self, the ever lurking imp in the ego is that of slyly insinuating a few deft pats on one's own back. This is the most pitiful sin of conversation. It is also a continuous temptation even to fine people. It is as persistent as original sin. Too few resist it well. It is the bad taste of much conversation. The more sly it is, the worse it tastes. The outright boast can be answered with a witticism. The sly pat on one's own back can only be swallowed with pity by those who love us, with contempt by those who don't.
A common device of those who are less clever is to apologize for their self-praise with the weak, "even if I do say so myself." A person should think twice before saying anything good about himself for which that apology seems to be needed. If a person feels that it needs to be added, he had better not inflict upon others that which an old