Continuing with Fulton Sheen's Victory over Vice, the good archbishop has this to say about Pride:
-- Victory over Vice, Fulton J Sheen.
Surely anyone who has had experience with the proud will bear witness to the truth of this statement: if my own eternal salvation were conditioned upon saving the soul of one self-wise man who prided himself on his learning, or one hundred of the most morally corrupt men and women of the streets, I'd choose the easier task of converting the hundred. Nothing is more difficult to conquer in all the world than intellectual pride. If battleships could be lined with it instead of with armor, no shell could ever pierce it.
On a related note, pride is sometimes manifest in refusal to serve; thinking that the one asking that service of us is not 'worthy' or 'beneath us'. "If God Himself, or the President, or the Pope asks me, then and only then I would do it." From another chapter ("Sloth"), this time about our laziness to work for Heaven, he wrote this:
Heaven is a city on a hill. Hence, we cannot coast into it; we have to climb. Those who are too lazy to mount can miss its capture as well as the evil who refuse to seek it. Let no one think he can be totally indifferent to God in this life and suddenly develop a capacity for Him at the moment of death.
Where will the capacity for Him come from if we have neglected it on earth? A man cannot suddenly walk into a lecture room on higher mathematics and be thrilled with equations if all during life he neglected to develop a taste for mathematics. And a heaven of divine truth, righteousness and justice would be a hell to those who never studiously cultivated those virtues here below. Heaven is only for those who work for Heaven.
Similarly, if we have refused to serve our brothers and sisters throughout our life, it will be inconceivable that we suddenly develop a capacity to serve God in Heaven...