She was in and out of prison four times for drug abuse, spending altogether six years behind bars.
Ms Tay Lee Leng, 61, decided that she needed to change only after realising that some fellow inmates had been in prison for many years.
"I told myself that I don't want to be like them," she said.
Since 2013, the social work assistant has been helping other inmates turn their lives around at The Turning Point, a halfway house for female offenders.
For Mr Michael Teoh, 53, his release after more than five years in prison - for robbery with grievous hurt - prompted him to pursue his dream of becoming a lifeguard.
Now a lifeguard as well as a swimming coach, he also counsels at-risk youth and continues to reach out to inmates.
These two former offenders are featured in the sixth episode of Heroes Among Us.