The 'Gravity' singer – who had an on/off relationship with the former 'Friends' star from April 2008 until March 2009 - is still struggling to come to terms with their separation, but still believes he did the right thing in ending their romance.
He said: "I've never really gotten over it. It was one of the worst times of my life.
"I have this weird feeling, a pride thing, for the people I've had relationships with. What would I be saying to Jen, who I think is f**ing fantastic, if I said to her, 'I don't dislike you. In fact, I extremely like you. But I have to back out of this because it doesn't arc over the horizon. This is not where I see myself for the rest of my life, this is not my ideal destiny."
Despite his reputation as a womaniser, the 32-year-old musician claims he is desperate to settle down.
He explained in an interview with Rolling Stone magazine: "I'll be happy when I close out this life-partner thing. Think of how much mental capacity I'm using to meet the right person so I can stop giving a f**k about it."
However, the musician is finding it difficult to meet someone new and claims he is constantly being rejected by the girls he approaches.
He said: "Blowing me off is the new s**king me off!"
Instead, the singer – who has dated a host of famous beauties, including Jessica Simpson and Cameron Diaz – wants to revisit his old flames in the hope of finding love again.
He added: "All I want to do now is f**k the girls I've already f***ed, because I can't fathom explaining myself to somebody who can't believe I'd be interested in them, and they're going, 'But you're John Mayer!' So I'm going backwards to move forward. I'm too freaked out to meet anybody else."