On Saturday, the Scottish singer-songwriter made his Glastonbury Pyramid Stage debut after canceling three weeks of work. He lost his voice and struggled with Tourette's syndrome tics, so the audience helped him finish his final song, Someone You Loved.
After his Glastonbury performance, the 26-year-old canceled all of his shows for "the foreseeable future" on Tuesday.
"I used to be able to enjoy every second of shows like this and I'd hoped three weeks away would sort me out," he said.
He added, "I'm so sorry to everyone who intended to come to a show before the end of the year but I need to feel well to perform at the caliber you all deserve.
This was my hardest decision because I've always wanted to play for you every night. I'll return ASAP."