Romeo considers love cruel and fleeting in Act 1, Scene 1-3 of Romeo and Juliet.
When the play begins, Romeo is moping. His parents and friends are worried about him, because he does not seem to leave the house. Romeo says that “sad hours seem long.” Benvolio asks him what makes them long.
Not having that, which, having, makes them short. (Act 1, Scene 1, p. 5)
Romeo’s problem is that his girlfriend has dumped him. He thinks there are too many hours in a day when he does not have love. He suggests that love is madness, and fleeting.
Love is a smoke rais'd with the fume of sighs;(190)
Being purg'd, a fire sparkling in lovers’ eyes;
Being vex'd, a sea nourish'd with lovers’ tears. (Act 1, Scene 1, p. 6)
Poor Romeo suffers because he thought he was in love, but his girl decided she wanted to be chaste. To him, love is fickle and changeable.
In a way, Romeo's complaints foreshadow what is about to happen. He is about to change his mind, and fall instantly in love with Juliet. Once he lays eyes on her, he seems to not care about Rosaline any more. So love is quickly changing, but this time it works in Romeo’s favor.
In Act I, scenes 1-3, Romeo finds love powerfully evil and painful. He says in Act I, "Alas, that love, whose view is muffled still, / Should, without eyes, see pathways to his will!" (lines 161-162). In other words, Romeo finds it cruel that love, which is blind, can still control his heart. He feels cursed by the power that love has to control him and the pain that unrequited love can cause him. He feels totally within the painful grasp of love and unable to fight its cruelty.
Romeo also considers love a kind of madness and refers to it as "a madness most discreet," or a wise kind of madness (line 184). In Act II, he says of himself that he is "not mad, but bound more than a madman is" (line 55). In other words, he is more constrained than a person who is tied up in a straightjacket. He feels that love has driven him to the point of insanity, and he feels less free to move than a man who has been tied up.