Othello was a character of changing attitude, depending on the situation. One thing about him did not change however: his love for Desdemona. As in all Shakespearian tragedies, however, the main character has one fatal flaw. In the case of Othello, this flaw also happened to be his love for Desdemona, but it is the love of a jealous man. Due to his love, and the deception of Iago, he was turned into a jealous monster that consumed him.
Throughout all the time he spent with her, he meant nothing with her, but eventually fell in love with her. He tells her father of his travels and battles and of his life in general, and while doing so Desdemona overhears. She asks him to speak of his life to her, and, as he puts it, "She loved me for the dangers I had passed, and I loved her that she did pity them.".
When Othello arrives in Cyprus, he brings good news of the Turkish fleet, but then his main attention returns to Desdemona. He spouts that her being there is the greatest joy of his heart, and he proclaims that even if he were to die then, it would be a happy death because she was with him. Such are the "ravings" of a love-struck man. Othello is also trusting, at first, of his friends, especially Iago. This trust puts him into position to be manipulated by Iago. Iago apparently hates Othello for both giving the honor of Lieutenant to Cassio, but he also believes that Othello has slept with his wife, Emilia. .
Due to the deception of Iago, Othello begins to become wary of Desdemona and Cassio. He meets Desdemona on the stairs and before he gets there, he sees Cassio depart from her, and becomes jealous, while saying nothing except to Iago. Iago later begins to fill Othello's head full of rubbish that Othello begins to believe, because he trusts Iago. Iago's words build upon the suspicion put into Othello's head by Brabantio, who said in Act 1, "Look to her, Moor, if thou hast eyes to see; she has deceived her father, and may thee.