Justin Bieber has opened up about the "terrible decisions" he made in the past and how he has managed to move on with help from God and some close people in his life.

The Canadian pop sensation said in an emotional post on Instagram that sometimes he had been so depressed it had been "hard to get out of bed in the morning". 

"When it feels like there's trouble after trouble after trouble. You start foreseeing the day through lenses of 'dread' and anticipate another bad day .... sometimes it can even get to the point where you don't even want to live anymore," he said. 

He continued: "You see, I have a lot of money, clothes, cars, accolades, achievements, awards and I was still unfulfilled." 

In the candid essay, Bieber revealed his fears of becoming another child star who would grow up with success only to struggle in adulthood, but also acknowledged that he didn't have the "humility" or sense of responsibility to deal with the fame and fortune that came his way as his music career skyrocketed.

"Everyone did everything for me so I never learned the fundamentals of responsibility," he wrote. 

"So by this point I was 18 with no skills in the real world, with millions of dollars and access to whatever I wanted.  This is a scary concept for anyone. 

"By 20, I made every bad decision you could have thought of and went from one of the most loved and adored people in the world to the most ridiculed, judged and hated person!" 

He said he could understand the struggles with drug addiction that so many stars experience because of the constant flip-flopping between everyday life and being on stage, with the entailing adrenaline rush. 

He said his own drug abuse turned him into a "shell of a person".

"I started doing pretty heavy drugs at 19 and abused all of my relationships," he said. "I became resentful, disrespectful to women and angry." 

He said he was fortunate to have people in his life who encouraged him to keep going as he paid tribute to his wife Hailey, a model and the daughter of actor and evangelist Stephen Baldwin whom he married last year. 

"It's taken me years to bounce back from all of these terrible decisions, fix broken relationships, and change relationship habits," he said. 

"Luckily God blessed me with extraordinary people who love me for me. Now I am navigating the best season of my life, 'marriage'!!  Which is an amazing, crazy new responsibility.  You learn patience, trust, commitment, kindness, and all of the things it looks like to be a good man." 

He ended by encouraging his 118 million Instagram followers to keep fighting even when the odds feel stacked against them. 

"Jesus loves you," he said. "Be kind today, be bold today and love people today not by your standards but by God's perfect unfailing love."