John Mayer "took a long time to get over" his ex-girlfriend Jennifer Aniston.
The rock musician and the actress began dating in 2008 and split for good three years ago.
John reportedly penned an ode to Jennifer on his upcoming album Born and Raised.
"[The song] Shadow Days is about Jen," a source told Us Weekly magazine. "It really took him a long time to get over her. He really loved her a lot."
John's lyrics speak of a painful split.
"You find yourself alone. . . I found myself in pieces/ On my hotel floor/Hard times help me see/I'm a good man with a good heart/Had a tough time, got a rough start/And I finally learned to let it go," he croons.
Shadow Days is a sincere adieu to their romance.
"He wrote the song as a farewell letter knowing [Jen] would hear it," the source added. "Ultimately he's done a lot of self reflection though and it he realises they weren't right for each other."
John previously dated Jennifer Love Hewitt and Jessica Simpson. The rocker is no longer interested in celebrity love affairs.
"He's looking for a nice, non famous girl he can relate to," the source said. "He loved [Jen and Jessica] both but it really affected him emotionally and it wasn't worth it."
Born and Raised will be released May 22.
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