On that day of the week and at that time of day people of one set, all acquainted with one another, used to meet on the ice. There were crack skaters there, showing off their skill, and learners clinging to chairs with timid, awkward movements, boys, and elderly people skating with hygienic motives. They seemed to Levin an elect band of blissful beings because they were here, near her. All the skaters, it seemed, with perfect self-possession, skated towards her, skated by her, even spoke to her, and were happy, quite apart from her, enjoying the capital ice and the fine weather. (1.9.5)
Such is the depth of Levin's infatuation that he is jealous of the people who are skating on the ice at the same time as Kitty.
Alexey Alexandrovitch was not jealous. Jealousy according to his notions was an insult to one's wife, and one ought to have confidence in one's wife. Why one ought to have confidence – that is to say, complete conviction that his young wife would always love him – he did not ask himself. But he had no experience of lack of confidence, because he had confidence in her, and told himself that he ought to have it. Now, though his conviction that jealousy was a shameful feeling and that one ought to feel confidence, had not broken down, he felt that he was standing face to face with something illogical and irrational, and did not know what was to be done. Alexey Alexandrovitch was standing face to face with life, with the possibility of his wife's loving someone other than himself, and this seemed to him very irrational and incomprehensible because it was life itself. (2.8.4)
It does not occur to Karenin to be jealous because he cannot stand the idea of his wife loving another man. Instead, he views his relations with his wife in the coldest, most rational way possible.
But he could not at once recall what he had been going to say. These fits of jealousy, which of late had been more and more frequent with her, horrified him, and however much he tried to disguise the fact, made him feel cold to her, although he knew the cause of her jealousy was her love for him. (4.3.17)
Anna's constant jealousy begins to severely alienate Vronsky.
[Anna:] "I'm not defending him, it's nothing to me; but I imagine, if you had not cared for those pleasures yourself, you might have got out of them. But if it affords you satisfaction to gaze at Thérèse in the attire of Eve..."
"Again, the devil again," Vronsky said, taking the hand she had laid on the table and kissing it.
"Yes; but I can't help it. You don't know what I have suffered waiting for you. I believe I'm not jealous. I'm not jealous: I believe you when you're here; but when you're away somewhere leading your life, so incomprehensible to me..." (4.3.24-26)
Anna is jealous, and doing a bad job of hiding it, even though she knows her jealousy is unreasonable and unfounded. However, having been isolated from the rest of society, she fears losing Vronsky as well.
"Why mine?" said Anna. "After yours I don't want another portrait. Better have one of Annie" (so she called her baby girl). "Here she is," she added, looking out of the window at the handsome Italian nurse, who was carrying the child out into the garden, and immediately glancing unnoticed at Vronsky. The handsome nurse, from whom Vronsky was painting a head for his picture, was the one hidden grief in Anna's life. He painted with her as his model, admired her beauty and mediaevalism, and Anna dared not confess to herself that she was afraid of becoming jealous of this nurse, and was for that reason particularly gracious and condescending both to her and her little son. (5.9.12)
Anna's jealousy is cropping up more and more often. Here she's worried that Vronsky is interested in Annie's nurse.
His jealousy had in these few moments, especially at the flush that had overspread her cheeks while she was talking to Veslovsky, gone far indeed. Now as he heard her words, he construed them in his own fashion. Strange as it was to him afterwards to recall it, it seemed to him at the moment clear that in asking whether he was going shooting, all she cared to know was whether he would give that pleasure to Vassenka Veslovsky, with whom, as he fancied, she was in love […]
[…] Levin's jealousy went further still. Already he saw himself a deceived husband, looked upon by his wife and her lover as simply necessary to provide them with the conveniences and pleasures of life.... But in spite of that he made polite and hospitable inquiries of Vassenka about his shooting, his gun, and his boots, and agreed to go shooting next day. (6.7.28, 36)
Levin is so easily jealous of his wife that his imagination runs rampant when Veslovsky indulges in some harmless conversation. Why is it that Levin believes that Kitty is in love with Veslovsky?
But without looking in the glass, she thought that even now it was not too late; and she thought of Sergey Ivanovitch, who was always particularly attentive to her, of Stiva's good-hearted friend, Turovtsin, who had helped her nurse her children through the scarlatina, and was in love with her. And there was someone else, a quite young man, who – her husband had told her it as a joke – thought her more beautiful than either of her sisters. And the most passionate and impossible romances rose before Darya Alexandrovna's imagination. "Anna did quite right, and certainly I shall never reproach her for it. She is happy, she makes another person happy, and she's not broken down as I am, but most likely just as she always was, bright, clever, open to every impression," thought Darya Alexandrovna, – and a sly smile curved her lips, for, as she pondered on Anna's love affair, Darya Alexandrovna constructed on parallel lines an almost identical love affair for herself, with an imaginary composite figure, the ideal man who was in love with her. She, like Anna, confessed the whole affair to her husband. And the amazement and perplexity of Stepan Arkadyevitch at this avowal made her smile. (6.16.18)
Dolly envies Anna's freedom and vitality in choosing to leave her husband, and she daydreams about having an affair and breaking out of the rut of her life. Later, after witnessing Anna's life close-up, she decides that she prefers her own life to Anna's. For more on this, check out Dolly's "Character Analysis."
"My love keeps growing more passionate and egoistic, while his is waning and waning, and that's why we're drifting apart." She went on musing. "And there's no help for it. He is everything for me, and I want him more and more to give himself up to me entirely. And he wants more and more to get away from me. We walked to meet each other up to the time of our love, and then we have been irresistibly drifting in different directions. And there's no altering that. He tells me I'm insanely jealous, and I have told myself that I am insanely jealous; but it's not true. I'm not jealous, but I'm unsatisfied. But..." she opened her lips, and shifted her place in the carriage in the excitement, aroused by the thought that suddenly struck her. "If I could be anything but a mistress, passionately caring for nothing but his caresses; but I can't and I don't care to be anything else. And by that desire I rouse aversion in him, and he rouses fury in me, and it cannot be different. Don't I know that he wouldn't deceive me, that he has no schemes about Princess Sorokina, that he's not in love with Kitty, that he won't desert me! I know all that, but it makes it no better for me. If without loving me, from duty, he'll be good and kind to me, without what I want, that's a thousand times worse than unkindness! That's – hell! And that's just how it is. For a long while now he hasn't loved me. And where love ends, hate begins." (7.30.4)
Anna knows that her jealousy is irrational, but she can't help it. Such is the nature of her desperate love of Vronsky.