"My greatest mistake right now is, I've been clinging to my art," he told the site. "In that, I have victory for my art and a great loss for my heart. At the moment, my beautiful fiancée is no longer my beautiful fiancée."
Mraz, 33, popped the question to on-again, off-again girlfriend Prettyman in December with a 2.3-carat diamond ring.
"Two halves don't make a whole," he told The Daily Beast. "Two wholes make a whole. In my relationship, I was giving myself away to make the relationship better, but in actuality, wasn't doing better by doing that. I became less of a man."
Mraz, who released the EP "Life is Good" in October, says he and Prettyman, 29, are still "super friends" despite the breakup.
"We go to yoga together, we surf together. We acknowledge the journey that each of us is on," he said. "We certainly want each of us to feel whole and complete. And it's when you're whole and complete that that attraction exists and it really thrives."