From cannabis to opium and even heroin, co-founder of the Breakthrough Drug Rehabilitation Centre in Selangor, Malaysia, Mr Samuel Krishnan had tried them all.
But in 2003, the 48-year-old co-founded the centre. He now works with former drug abusers and helps them kick the habit for good.
"Many abuse drugs to forget their troubles. But what they don't know is that their troubles will only get worse when they start taking drugs," said Mr Samuel, who is now the proud father of three boys and a girl, who are aged between seven and 13.
He had started experimenting with cannabis when he was 15 due to peer pressure.
Back then, he liked to spend his days hanging around with a group of young neighbourhood delinquents. They introduced the drug to him.
He started as a casual user, but went on to sell the drug three years later.
When he was 20, he was arrested for the first time when he was caught in possession of cannabis. He was released after paying a fine of RM1,000 (S$390).
That brush with the law did not deter him from abusing drugs - he switched to heroin about a year later.
In 1988, he tried to change for the better and packed his bags for Singapore where he worked as a storekeeper.
But five years later, his habit returned to bite him.