Sometimes absence makes the heart fonder than its object deserves. . . .
Jane is delighted to meet someone again. Perhaps it's Jill, her Best Friend Forever in school; perhaps it's Jack, whom she was engaged to, and whom she has waited for.
Within minutes of their meeting, she realizes this is a big mistake. One or both of them have changed too much, or she realizes things she had never seen before, or it becomes apparent that the reality does not live up to the fantasy. In an inversion of Oblivious to Love, Jane may realize that she has long fallen out of love, and quite often, that she was Oblivious to Love in a third character.
Tends to be treated far more sympathetically than Absence Makes the Heart Go Yonder. Inverse of New Old Flame.
Compare Growing Up Sucks if the two met as children.
An episode of Rumic Theater has a man being invited to a school reunion by a girl he remembers having a crush on, and who might just have reciprocated, but he was transferred out before he could learn the truth. His current married life is...disappointing, and he fantasizes about having a fling while simultaneously realizing how unlikely that would be.
At the reunion he meets the woman who reveals that she did have a crush on him, and is conveniently recently divorced...and is now grossly overweight, not one bit pretty and a sloppy drunk. He decides to bail out early. On his way to the train, the man meets the actual girl he was thinking of (both women have the same given name) who is just as pretty and likeable as he remembers...and is happily married with several children who made her late for the reunion. He returns home somewhat heartened and determined to make his own marriage work.
In P. G. Wodehouse's A Damsel In Distress, Maud meets her beloved Geoffrey — who's turned fat and obsessed with food, and her heart is breaking at the thought she has pledged herself to him, when he gets a break of promise suit served on him. She goes off to find the man who helped her meet him and propose marriage.
In Dorothy L. Sayers's Gaudy Night, Harriet Vane goes to Gaudy Night to meet an old school friend. Within minutes, they are making painfully polite inquires about the other's life, and Harriet is thinking it's terrible, and she should never have come.
Jocelyn left her husband on her wedding night because she had fallen in Love at First Sight with the best man. When he returns and is not the stuff of romantic dreams, she reconciles with her husband.
When Noel has jilted Gay to take up with Nan, and Nan has jilted him in turn, he comes back to Gay. She realizes how false he is, and laughs.
Eva Ibbotson's Dial-a-Ghost has the son of the ghost family portrayed with a long term crush on a Cynthia Harbottle. When she turns up as a ghost in the final chapter, she is old, plump and selfish.
In Edgar Rice Burroughs's Fighting Man of Mars, Tan Hadron has this twice: the first time, he convinces himself that the woman is just dispirited from her captivity, but the second time, he realizes the truth and repulses her.
In Jack Campbell's The Lost Fleet series, an old love of Captain Desjani is one of the prisoners they rescue. Desjani soon realizes that he changed in the prison camp, and he starts to have an affair with a subordinate, for which he was transfered.
In Dreadnaught, Rione has more than a touch of this with her husband, long a prisoner of war.
In P. G. Wodehouse's Jill The Reckless, Jill had deliberately thrown herself into work, far from Derek, to recover from him, and just before the meeting, noted that it had worked. Nevertheless, meeting him again reinforced that.
In Nick Hornby's High Fidelity the main character has never really got over Charlie, the girl that broke up with him at university. When he meets up with her again years later, it takes a few hours for him to come to the conclusion that "Charlie's awful".
In Katherine Paterson's Of Nightingales That Weep, at the end of the novel, Takiko's ugliness from hard work in the outside instantly repel a man who had been attracted to her beauty.
How I Met Your Mother: After years of searching, Ted found the "Slutty Pumpkin," a girl he fell in love with at a party but he never saw again. Both Ted and the girl found the relationship awkward, but neither wanted to break it off because they thought the other person was into the relationship.
Friends: Monica's situation, when she runs into her Richard after a painful break up several years before. Her boyfriend Chandler, freaks out, thinking she's still crazy about Richard, but Monica's first reaction is that she feels nothing for Richard anymore and there are No Sparks.(Of course convincing Chandler of this, is a whole other mission.)
Shameless (US version): Fiona starts flirting with the guy she had a crush on in high school, but once the have a very awkward sexual encounter Fiona doesn't feel the same anymore.
This happens for Scully in The X-Files in episode "all things". In medical school, she had an affair with a professor. Once she found out he was married, she was horrified and left her medical career to join the FBI. Ten years later, she runs into this professor, who is in the hospital for a heart condition. She is understandably perplexed as to why he's in Washington D.C., and he explains that his wife is now dead and he's come to invite her to run away with him. However, Scully is now ten years older, wiser, and has a life of her own now. It's an episode that is a major reality check for Scully about where her life has gone and what it could have been. In the end, she turns down the offer and realizes she likes the way her life has turned out. This also marks the start of Mulder and Scully's sexual relationship. Probably.