According to Men's Health, a guy who talks alot about himself will leave you feeling lonely and alone. They listed these behaviors of a man who thinks too highly of himself:
Brags about past conquests in front of you and your freinds
Waits until the last minute to ask you out, assuming you don't have plans
Is convinced he knows more about you and your anatomy/job/family than you do
Never admits he's wrong.
Always "lets you win" at pool, video games, ect. . .