If you're going to break your friend’s heart by choosing his romantic rival, make sure to let him down easy by explaining that you're still in love with him.
At the end of Eclipse, Bella has to make a final decision between her two suitors: Well-heeled vampire Edward and Thoreauvian werewolf Jacob. The fact that she chooses Edward is already a disappointment for Jacob, but then Bella explains that she actually does love Jacob... she just loves Edward more. According to the Transitive Property of Love in the Time of Cholera, this ensures that Jacob will be eternally devoted to Bella Swan. Which could get awkward...