In her upcoming memoir "Open Book", Simpson wrote about what she learned about herself from her relationships, including her romance with Mayer whom she met in early 2005 at a Grammy party.
The guitarist told her how much he admired a song she wrote called "With you", and she was flattered when he began to write notes to her.
After she divorced singer Nick Lachey in late 2005, she began dating other men. Mayer told her "he wanted to have all of me or nothing".
"He'd walk into a room and pick up his guitar and you'd swoon," Simpson told people.com.
"I didn't really know the man behind the guitar. And that was my mission."
They dated in secret for several months and she fell in love with his intensity. "Again and again, he told me he was obsessed with me, sexually and emotionally," she wrote.
There were times when she felt insecure around him too.
"I constantly worried that I wasn't smart enough for him," she wrote. "He was so clever and treated conversation like a friendly competition that he had to win."
She was so afraid of disappointing him that she sometimes had a friend check her texts for correct grammar and spelling.
And when she felt unsure of herself, her "anxiety would spike and I would pour another drink. It was the start of me relying on alcohol to mask my nerves".
"He loved me in the way that he could and I loved that love for a very long time," she said of Mayer. "Too long. And I went back and forth with it for a long time. But it did control me."
Their contact ended after he called her a "sexual napalm" in a 2010 interview. "He thought that was what I wanted to be called," she said. "I was floored and embarrassed that my grandmother was actually gonna read that."
"A woman and how they are in bed is not something that is ever talked about," Simpson added. "It was shocking."
The hardest part was learning Mayer had broken her trust. "He was the most loyal person on the planet and when I read that he wasn't, that was it for me," she said. "I erased his number. He made it easy for me to walk away."
Although they are no longer in touch, she said: "I know that he's publicly apologised and I don't want to take that away from him. I think he knows a lot of this about me already but he doesn't know the perspective I have as a woman. That was Jess in her 20s."
( With inputs from IANS )