"My Happy Ending" is a song written and produced by Avril Lavigne and Butch Walker, and engineered by Russ T. Cobb for Lavigne's second album, Under My Skin (2004). It was released as the album's second internationally released single in 2004 and became Lavigne's fourth most successful single. It peaked higher than "Don't Tell Me", the album's first single. In the United Kingdom, it reached the top five; in the United States, it peaked at number nine (staying in No. 9 for 4 weeks). Structurally, the song is written in 4/4 style and has a repeated hook in both the chorus and in the intro and outro.
The music video for "My Happy Ending" was written and directed by MTV and Grammy winner Meiert Avis. It was shot on location in Williamsburg, Brooklyn and Harlem, New York City. The video begins with Lavigne running down a street and entering a cinema, where she finds the film playing is a montage of her memories concerning a specific relationship she had. At first, the memories (shown in full color) are happy, depicting Lavigne at the park with her boyfriend, as he hands her a flower and they laugh together. They are also shown goofing off inside a laundromat. However, as Lavigne sings "so much for my happy ending," the memories start losing color. Lavigne and her boyfriend lie in bed together, as she looks at him and he (obviously reeling from a disagreement) stares blankly away. The relationship culminates during the song's bridge inside a grocery store, where her boyfriend antagonizes her, insisting that he talk to her. He grabs her and tries to pull her into his embrace. Fed up, she turns and pushes him away. She proceeds to run out of the grocery store and down the street (from the beginning of the video), and to a guitar shop where she grabs a guitar and walks to the roof of the building, where she is seen performing with her band. There, she walks past her unapologetic boyfriend without looking at him. The theater film tears and the memories end, leaving the final seconds of the video as a close-up on Lavigne in the theater as she tries to decide if the break-up is happy after all. In the end, three other girls witnessing in the restaurant leave with Lavigne who know about the breakup as they befriend each other.
Lavigne said of the video: "It's about a relationship that doesn't work out, and having to say goodbye to all of the memories and... all that stuff." When asked if the video for "My Happy Ending" actually contains a happy ending, Lavigne said: "I don't know if the video has a happy ending. It kind of depends on how you look at it? In one way, it is because me and 'the guy' in the video aren't together anymore, and I think that's a better thing."
David Browne of Entertainment Weekly magazine commented "Lavigne herself sounds more burdened; ... the sk8erboi of the first album has turned out to be a selfish, nasty creep who ... treats her like crap".Allmusic highlighted the song as a "track pick" in a review of the album, Under My Skin. Blender also did the same. PopMatters thought "The second single, "My Happy Ending", suffers from a marked similarity to a few recent hits, notably Michelle Branch's "Everywhere" and Vanessa Carlton's "A Thousand Miles" (...) The ticklish good humor of "Sk8er Boi" has been subsumed by the sardonic regret of "My Happy Ending".
In an AOL Radio listener's poll, "My Happy Ending" was voted Lavigne's third best song.
As of July 2013[update], "My Happy Ending had sold 1,093,000 digital copies in the US.