Keenan Mundine was 14 when he first went to juvenile detention for breaking into a car to steal a laptop. He is now 31 and has spent more than half of his life behind bars.

Since leaving prison three years ago he has turned his life around and is now a youth worker for at-risk youth, starting up Inside Out Aboriginal Justice Consultancy.

He told The Drum three things he knows about prison and getting out.

1. Prison can be lonely

Despite fellow inmates knowing who he was, those were the loneliest times of his life.

"I was in cells with four other guys … but I still felt alone. I still felt by myself."

"You go to prison on your own. You come out on your own. You get locked in on your own."

He lost his parents at the age of six, and a year later was separated from his older brothers.

"For me my loneliness was around my family and feeling lost and my identity and not knowing who I was."

Mundine grew up on the streets of Redfern, NSW, in an area known as "The Block".

He looked up to the men who seemed to have it all.

"They had the nice shoes, they had money, they had watches and chains, they had phones, everything that a young guy looked up to and strived to be like."

He thought he had found his identity, finding a "certain sort of camaraderie from hanging around these people in the community".

"They were doing stuff, so I wanted to be involved. I would do it to win points with the crew."

He saw them as tough guys or warriors.

Now, with time, he thinks tough guys are those who look after their family and do not harm others to do it.

"You worked hard like everybody else, you didn't lie, steal and didn't take what wasn't yours."

2. Prison never leaves you

Mundine worries about his former life.

When he wakes up in the morning there can be a split second when he thinks he is still in a cell.

"I always worry about that life. You know a big portion of me was that life."

"I sleep at night and I still hear doors getting opened, people yelling and screaming. I still feel or wake up and feel like I am in a prison cell, even though I know I am at home with my family."

Mundine wakes up some mornings still thinking he is in a cell. ( The Drum )

Now an advocate, Mundine has told the United Nations Human Rights Council in Geneva he could still smell the tiny prison cell he was first locked in.

This year about 600 children under the age of 14 are serving sentences in youth detention.

"I am always hyper-vigilant about my surroundings and where I am, and I know that I will never ever, ever have to commit a crime again to look after myself, to take care of my family."

3. The 'catch me if you can' lifestyle catches up

Mundine spent 15 years in and out of the criminal justice system — the longest stretch was four years.

Each time he was released he would go back to the streets, take drugs and alcohol and the cycle would continue, he said.

"That sort of became normal to me that you either end up in prison or you die or you go play football, that's the only way out of my community."

Mundine said he had not felt like there was anywhere he could go, and did what he thought he had to do to live.

"That was my trade, that was how I was taught to look after myself. There were people who could go home to their family or had support and leave that stuff on the street."

He warned those who thought the lifestyle would not follow them into adulthood and affect their future opportunities were deluding themselves.

"My attitude at the time was sort of 'stuff the world,' and 'come and get me,' that attitude really came back to bite me in the bum not just as a juvenile but as an adult as well."

Mundine is now a youth worker and wants others to know they could change their lives.

"I don't think it's cool.