Steven Beattie spent his teenage years in and out of Polmont young offenders' institution, once described by a former governor as "the most violent prison in Scotland", external.
He was sent there at 16 after drunkenly crashing a stolen car, and returned repeatedly over the next four years as his involvement with gangs and violence grew.
For Steven, the turning point came when he was punished for his part in a fight by being locked up for 23 hours a day and having his TV removed.
"I never really had time to sit down and think where my life was going," he told the BBC's Scotcast podcast.
"When they took my telly, I finally had that opportunity."
He asked himself - if he kept doing what he was doing, where would he be in five years' time?
"If I don't like that destination, I'll have to change it," he says.
"I wrote out a plan and I stuck to it."
Steven admits it wasn't easy for a young offender to start a new life but, after years of effort, he's about to graduate as a resident doctor.
Steven, who is now 37, grew up in the Hillington area of south-west Glasgow.
His father had the degenerative disease Parkinson's, and his mother was diagnosed with paranoid schizophrenia as well as cancer, from which she later died.
"I was under a lot of stress at home," says Steven, who was a carer for both his parents.
He left school at 15, and thinks few of his teachers understood how much stress he had been under because he had been "embarrassed" to tell them.
Looking back, he gives himself "a degree of sympathy" that he didn't do so well in school because of what he was dealing with at home.
"A lot of the time I couldn't make school because I was up to three in the morning looking after my parents," he says.
Steven says avoiding gangs was "impossible" where he grew up in the 1990s and early 2000s, as "gang violence was rife".
The threat of a spell in Polmont kept him out of trouble for a while, but once experienced, its deterrent effect disappeared.
He made close friends while inside and, at first, life there wasn't as bad as he had feared. But he struggled to cope with the relentless noise, especially when he was trying to sleep.
"You've got people kicking your doors and constantly shouting and screaming, and people are in there for months and sometimes years," he says.
"You can imagine the effect it has on a developing brain, being in that environment for years at a time."
Eventually, Steven made a decision to change his life and wrote down three things he had to do - leave Glasgow, quit drinking, and stop hanging around people who got into trouble.
When he left Polmont, he thought most employers would find it difficult to trust him, so he started his own personal training business. He is also an award-winning MMA fighter known as 'Doctor Beatdown'.
Working for himself gave him the ability to save up and move out of Glasgow. But his long-term goal was to become a doctor.
He had been inspired by his dad's neurologist, who had noticed how much Steven was able to understand about his father's Parkinson's.
His school grades were not enough to get him into medical school, so he attended an access course at Glasgow Kelvin college to study physiology at the University of Glasgow.
That then got him into medical school, and in June, he'll graduate as a resident doctor. He hopes to specialise in either surgery, neurology or emergency medicine.
