flatter oneself

flatter oneself

Be gratified vainly by one's own achievement; exaggerate one's good points. For example, He flattered himself that his presentation at the sales conference was a success, or She flattered herself that she was by far the best skater at the rink. This usage is often put negatively, as in Don't flatter yourself-we haven't won the contract yet. [Late 1500s]
See also: flatter