We're all familiar with what happens when a writer's personal problems start to intrude upon their work - characters are killed off left and right, plots are resolved either in a depressing fashion or not at all and the worldview espoused by the work as a whole seems much bleaker than it was before.
But what happens when the opposite happens? Whether by dint of marriage, the birth of a child, the author finding religion or some other cause, the author now finds themselves in a much happier place than they were before. And, hardly unexpectedly, this starts to bleed into their work, which becomes Lighter and Softer and much more optimistic.
Just as Creator Breakdown isn't necessarily a bad thing (many artists produce their best work while feeling down in the dumps), this trope isn't necessarily a good thing either: feeling happy and self-satisfied can often lead to an artist becoming complacent and unwilling to push themselves creatively. On the other hand, a sunnier disposition may result in an author cutting down on the Wangst.
This is the Opposite Trope to Creator Breakdown and, just as with that trope, Word of God examples are required for it to qualify.
See also Tone Shift, Lighter and Softer, Darker and Edgier and True Art Is Angsty.
Anime & Manga
Neon Genesis Evangelion is a dark, psychological deconstruction of Mecha anime about loneliness and despair created when Hideaki Anno was suffering from clinical depression. Cue being married and recovering and all of a sudden we get a retelling in a series of movies by the same guy, called Rebuild of Evangelion trying to make the story make more sense and have less of a Downer Ending. Hmm...coincidence?
He's certainly had a recovery, but it's too soon to come to any conclusions about the direction this reboot is going. He could just be trying to show that even when he's in high spirits and leading a well-adjusted life, he can still take an audience in his hand and crush it.
In-universe example: Ryu Shizuka from Bakuman。 writes dystopian fiction, but after his editor takes him to a cabaret where he talks to women for the first time, his main character slowly develops into a Mary Sue who spends most of his time with a harem of hot women. After the editor shows him the women were only nice to him because they got paid, Shizuka becomes disillusioned again and continues writing about how all Humans Are Bastards (even women).
Gen Urobuchi. In Fate/Zero's afterward he wrote that he wanted to write a heartwarming story one day, but couldn't because of his "tragedy syndrome". Then came Puella Magi Madoka Magica where he does manage to write something heartwarming exactly as he described in the Fate Zero's afterward. Since then, his later works have fallen more on the idealistic end, such as (the admittedly still dark) Psycho-Pass and Suisei no Gargantia. It probably helps that Madoka Magica has put him on the map as a writer of television shows. Even when he wrote one of the darkest Kamen Rider shows ofThe New Tens and changed the ending to Madoka to something more dark, they managed to be idealistic to a degree.
Alan Moore has admitted that he was going through a period of depression and disillusionment when he wrote Watchmen, but he eventually got over it. Almost all of his major works after Watchmen (with the exception of From Hell) have been more optimistic and light-hearted than that one.
Cathy Lee Guisewite, creator of comic strip Cathy, often jokes that her boss at the syndicate dreaded the day she entered a stable relationship and became a more secure, confident person. When just that happened, Guisewite chose to end Cathy rather than let it fall victim to this trope.
When Harry Met Sally: Rob Reiner got the idea for the film after a divorce and a string of complicated relationships before then. He met his next wife while developing the film, and their marriage inspired him to change the ending so Harry and Sally do get together after all.
David Drake is a good example: his fiction after Redliners is less harsh and more optimistic, with a little more faith in humanity. Author's comments.
The tone of Anne Rice's fiction became significantly more positive when she converted to Christianity, as she herself acknowledged:
“My faith in Christ is central to my life. My conversion from a pessimistic atheist lost in a world I didn't understand, to an optimistic believer in a universe created and sustained by a loving God is crucial to me.
Barry McGuire is best known for his depressingly cynical song, "Eve of Destruction". His best known post-spiritual-conversion song is "Cosmic Cowboy", an optimistic song with Jesus in the title role.
Pet Shop Boys' album Very was more upbeat and exuberant than their prior albums, owing to singer/lyricist Neil Tennant being in love at the time. It is sometimes referred to as their "coming-out" album, as Tennant had begun openly discussing his homosexuality for the first time during this period.
Billy Joel's very upbeat and poppy An Innocent Man, a tribute to Joel's musical influences from The Sixties, followed the cynical, sociopolitically charged The Nylon Curtain. While TNC was recorded during Billy's divorce from his first wife, AIM was a product of then-single Billy enjoying life as a bachelor and dating a number of supermodels, most notably his future second wife Christie Brinkley.
Starflyer 59's album Gold was written and recorded while Jason Martin was on the verge of a nervous breakdown, due to the messy ends of several friendships and the stress of recording the album practically by himself. For the followup album, Americana, Jason Martin had a full band playing with him and producer Gene Eugene to help with the duties of recording, so it was a much more "fun" rock album. It's probably not a coincidence that Jason switched to playing New Wave music and almost entirely abandoned guitar distortion shortly afterwards.
Charlie Brooker, as indicated in the page image, stopped writing "Screen Burn" around the time that he got married to Konnie Huq, realising that it would fall into this trope on account of him no longer being countercultural and miserable, and saying the writer to take over was a better fit for it now as she was "pure hate". He carried on writing opinion pieces, but even in those he remarked in that the tone of his work got a lot lighter as his life improved and he just couldn't work up the level of hatred required any more - even realising around the time he had a kid that he Became His Own Antithesis as being an avowed Child Hater is a constant theme of his work. On the other hand, he did announce his new fatherhood a whole column about how much he loved babies with a preceding paragraph explaining he was doing it entirely tomake his fans angry, so he's not all nice.
In 1979, Richard Pryor went on a trip to Africa, and was so moved by the solidarity of the people there that he renounced his legendary N-Word Privileges. As he explained in his 1982 comedy special Live at the Sunset Strip:
Richard: I asked myself "Do you see any niggers?", and I said "No, because there aren't any..."