At the beginning of the play, both characters at least profess to abandon themselves to their emotions. Orsino embraces the extreme depth of his love, praising the "spirit of love" for how much it can devour. Valentine says that Olivia's servant Maria has told him that Olivia will walk around her room twice a day crying to mourn her brother. When we actually see Olivia, however, she at first seems much more dignified and restrained than Orsino. She doesn't reveal to "Cesario" how she feels about him at first. When she does in act 3, her oath is by all modest things: "Cesario, by the roses of the spring / By maidhood, honor, truth, and everything / I love thee so that maugre all thy pride / Nor wit nor reason can my passion hide." She is not able to contain herself, but unlike Orsino, she believes that she should. ("Maugre" means "despite.") At the end of the play, when she sees Orsino in person, she reminds him of the rules of noble behavior:
ORSINO What shall I do?
OLIVIA Even what it please my lord that shall become him.
This statement is Olivia calling on Orsino to behave in a dignified and controlled fashion, which he certainly does not, as immediately afterwards he threatens to kill Cesario. Whereas Orsino is committed to expressing the excess of his emotions, Olivia believes in a noble restraint, even if she is not always able to follow through on that belief.