The desire to undertake, or the actual undertaking of, what is above one's capacity. It is a result of pride, which makes a person overestimate his abilities and blinds him to his deficiencies. It also leads one to expect graces from God without doing anything to obtain them, and even when acting the opposite, as when sinning, the person presumes that forgiveness is assured. (Etym. Latin praesumere, to suppose, take for granted.)
That makes perfect sense.