"It's like he's stuck in the rock 'n' roll lifestyle. It used to be so much fun, but he's beginning to feel unfulfilled. And the exhaustion is starting to show.
"The pressure and uncertainty are getting too much for Harry. He needs to take care of himself but he just wants to party through everything," a source said.
Things haven't been easier for departing member Zayn Malik, who quit earlier this year to have a "normal" life, as he is allegedly "freaking out" over a leaked demo he recorded.