Justin Bieber. Picture: Bang Showbz

Justin Bieber is reportedly doing "better already" after cancelling the remainder of his world tour and has been working on getting "stronger mentally".

The 23-year-old singer scrapped the remaining concerts on his 'Purpose' tour last month due to "unforeseen circumstances", and has been focusing on his "spiritual journey" in order to help himself to get "stronger mentally".

A source told People magazine: "He started out in the business as a kid, but he is older now. He wants to have control over his life and health. He hasn't been feeling well mentally for a while. Canceling the tour was the right thing for him.

"He needed to take a break and just focus on himself. He is doing better already. He is focused on his spiritual journey. He wants to be stronger mentally."

Following his decision, the 'Sorry' singer penned an emotional open letter to his fans last week to explain why he needed to take a break, and he decided to write the note because he felt "bad" to have left so many of his loyal supporters disappointed.

The insider added: "Justin is hanging out in LA with friends. He feels really bad to disappoint many of his fans.

"This is why he decided to write the open letter. He still feels he made the right decision."

The Canadian pop star revealed in his message he needed to take time away to work on making his his "mind, heart, and soul" are "sustainable".

He explained: "Me taking this time right now is me saying I want to be SUSTAINABLE.. I want my career to be sustainable, but I also want my mind heart and soul to be sustainable. So that I can be the man I want to be, the husband I eventually want to be and the father I want to be. 

"This message is just an opportunity for you to know my heart, I'm not expecting anyone to understand, but I do want people to have an opportunity to understand where I am coming from! THIS MESSAGE IS IS VERY GRAMMATICALLY INCORRECT BUT ITS FROM THE HEART. BUT I ITHINK THERES SOMETHING SPECIAL ABOUT IMPERFECTIONS!!" (sic)"