Per Refinery29, John Mayer and Jessica Simpson met while she was still married to Nick Lachey, and after she and the 98 Degrees star finalized their divorce in 2006, Simpson and Mayer started a relationship that turned out to be one of the most tumultuous celebrity unions of the late 2000s.

In an excerpt from her memoir, "Open Book," in which she dishes all about her relationship with Mayer, the fashion mogul got candid about how she felt inferior to Mayer pretty much from the get-go, writing that she was afraid that she wasn't "smart" enough to keep up with him. "He was so clever and treated conversation like a friendly competition he had to win," she wrote. "One minute he was explaining the start of his Rolex collection, and then another he was going on about a collector who he was jealous of, then the nature of jealousy, then the concept of time and the heft of it on your wrist...."

In an interview with "TODAY" while promoting her memoir in 2020, the "Employee of the Month" star opened up even more about their relationship, telling Hoda Kotb, per Entertainment Tonight, "We were great at intimacy. We were great at loving each other. That was easy, but the relationship was very complex. And it was always on-again, off-again. On-again, off-again. And I went back close to nine times." Simpson also noted that Mayer broke up with her via email most times.