John Mayer took ''days and days'' to record one line for a song because he couldn't stop crying.

The 39-year-old singer - who has dated Taylor Swift and Katy Perry in the past - insists he will never be able to play heartbreak song 'Never on the Day You Leave', from his latest album 'The Search For Everything', live because the ''brutal'' lyrics make him break down.

He said: ''There's a line in there that is so brutal because it's so true and I can't play the song live because I don't think I'd make it through it.

''Every time I sang that line, I would cry in the middle of that line.

''It took me days and days and days to be able to sing that line for the record, and get through it without crying.''

The line in the song, which only took John 20 minutes to write, he is referring to reads: ''She'll fight for you like hell, then force herself to like some other man.''

John didn't name the ex he's written about but admits he recently had an ''amicable'' conversation with her following their ''hard'' break up.

Speaking on SiriusXM Radio's 'The Highway' show, he added: ''Not long ago, I ran into my ex. It was very amicable. And I had this beautiful moment where I said, 'A lot of it's me.'

''A lot of it is in my head, you know. Like, something happened to me and it's just the way I work. It's the way my mind is and I took it really hard. And that took a long time to be able to admit.''

Earlier this month, John was romantically linked to actress Amy Schumer, and the pair are said to have gone on a few dates.