U2 star Bono pours so much emotion into his stage performances, he suffers what his family call "gig lag" for days after he completes a tour.
The Irish rocker struggles to sing his songs live unless he is in exactly the right frame of mind - and it means an exhausting rollercoaster of emotions.
He explains: "I can't sing in the registers that I sing in. So I really have to step inside the song or else I'm not going to be able to hit some of those notes.
"It's not a glorious dedication to the art. It's just a necessity. I probably think if it wasn't that way, I might try to fake it."
But performing at 100% every night takes its toll on Bono when tours end and he's back home with his family.
He adds: "In a U2 show there's a lot of different feelings you're going through.
"My family refers to 'gig lag', where the coming down off that can be unpleasant. I am as high as a kite the day after, but the next day I can really hit a wall."