many criminals find it incredibly hard to "go straight". Often they only do so after being hit by a life-changing event - a lengthy spell behind bars, for instance.
In the case of former football hooligan and gangland thug Carlton Leach, it was the execution of his friend, Tony Tucker, in the infamous Range Rover murders at Rettendon.
In the wake of the gangland slayings which rocked the Essex underworld, Leach says he turned his back on a life of violence, underworld deals and drug abuse.
Now he is hoping his experiences on the wrong side of the law will help turn youngsters away from a life of crime.
Leach was catapulted into a criminal career by his love of West Ham United. Before long, he was a member of the notorious Inter City Firm - a gang of hooligans who followed the East London club.
Soccer violence provided his first taste of the criminal world. He recalled: "I got into football at an early age and that was all I lived for. The football violence came with it as the years went on.
"When we first started going as kids, in the Seventies and Eighties, it became massive and the people around at the time got involved. It was part and parcel of supporting your team - fighting for them.
"But it wasn't as bad as people make out.
"It was more like grown men chasing each other and every now and then, someone getting seriously hurt.
"With 300 men throwing punches, every now and then, one is going to make contact."
For Carlton Leach, that contact once came in the form of a knife in the back of his head from a rival football yob. His brother-in-law almost died in a stabbing incident.
After ten years as what he describes as "a hardcore hooligan", Leach, who was born and bred in Canning Town but now lives in Southend, decided he'd had enough of football violence.
But his fearsome reputation went before him and he was soon working as a bouncer in the tough clubs of East London.
It was during his time as a doorman he moved on to the illegal rave scene and was drawn into the burgeoning trade in drugs - particularly ecstasy.
Leach and his fellow bouncers provided the security at events and acted as minders to those peddling the illicit substances.
Leach said: "Our wages went from £50 a night to £200, to £300.
"We started doing very big raves and had to accept you had to turn a blind eye to the drug-dealing. The raves wouldn't have happened without the ecstasy.
"To some extent, you just had to go with the flow.
"As the drug scene exploded, I started supplying the muscle for drug deals and collecting the money."
It was around this time he met Basildon drug dealer Tony Tucker. The pair became close friends and both were drawn even more deeply into the murky world of drug-dealing.
He and Tucker developed a strong bond, he said.
"We had respect for each other. The real Tony wasn't a drug dealer. He was a successful businessman. You could trust him and behind closed doors, he was very lovable - like a brother."
Their friendship came to an abrupt and bloody end in December 1995, when Tucker and fellow dealers Pat Tate and Craig Rolfe were blasted to death in a Range Rover on a farm track in Rettendon.
The murders changed Leach. He went from a fearsome hard-man to being terrified he would be next one to take a bullet.
He said: "For four to five years after the murder, I lived a very paranoid life. I didn't trust people and locked myself away.
"At the end of the day, me and Tony lived a similar life and took similar chances.
"After the murder, I had to change my life. It was a wake-up call - to realise I had a mum and dad and a family. When I saw how it affected them and my life, I realised I had to grow up."
Leach's story was recently told in the film, Rise of the Footsoldier. But he says the lessons he learned should persuade young people to steer clear of a life of crime.
The ex-gangster - now 49 and a father of six - said: "Kids are too easily impressed by films they see, like Snatch and Football Factory.
"They think they want to be like those gangsters, but it doesn't necessarily mean you have a great life.
"There is a lot of pain in being involved in drugs and violence and there is a price to pay."
He added: "I want young people to be influenced by my life story in a good way.
"If I catch them at the right age and persude them, it'll be a good thing.
"It's not glitzy or glamorous.
"The people around you won't be safe, you will put your loved ones through a lot of pain - and it can cost you your life."