EXCLUSIVE: Why Justin Bieber Canceled His 'Purpose' Tour

An aggressive tour schedule has taken its toll on Justin Bieber, sources tell ET.

On Monday, the 23-year-old superstar announced he's canceling the remaining dates of his Purpose tour, citing "unforeseen circumstances." Bieber had at least 12 concerts left on his schedule, including an Aug. 5 performance at the Rose Bowl in Pasadena, California, which he had given out tickets to an entire audience of The Ellen DeGeneres Show for.

A tour source tells ET that Bieber is currently "exhausted."

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"This is a guy who has had 150 shows on this tour, on six continents, over the last year and half, and he's tired," the source says. "He needed a break and as much as he didn't want to disappoint his fans, the best decision for him was to cancel the remaining tour dates."

A second source tells ET that Bieber very much had his fans in mind while making the decision.

"The tour was just really long and he was exhausted," the source notes. "He doesn't want to let his fans down but they have always had his back."

A statement on Bieber's official website on Monday thanked fans on behalf of the "Sorry" singer, and said ticket refunds will be available at the point of purchase.

"Justin loves his fans and hates to disappoint them," the statement read. "He thanks his fans for the incredible experience of the Purpose world tour over last 18 months. He is grateful and honored to have shared that experience with his cast and crew for over 150 successful shows across six continents during this run. However, after careful consideration he has decided he will not be performing any further dates."

The Purpose tour kicked off on March 9, 2016 in Seattle. His last show was in London, England on July 2.

There have been signs that Bieber has been struggling on tour. Last March, Bieber canceled the meet and greets on his tour, explaining that they left him feeling "drained and unhappy."

"Want to make people smile and happy but not at my expense and I always leave feeling mentally and emotionally exhausted to the point of depression," he Instagrammed.

Last October, he walked off stage after fans booed him in Manchester, England, and was growing increasingly vocal about his displeasure with screaming audiences during his shows. Still, he extended his tour dates that same month.

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However, it's clear Bieber still has love for his fans. Last week, Bieber made a surprise visit to the Children's Hospital of Orange County, sans any entourage or press.

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