For someone who dropped out of primary school and started out as an unlicensed street hawker, Mr Lock Meng Swee has come a long way.
Up until his retirement 17 years ago, he had never obtained formal educational qualifications.
"I went to primary school but I never graduated," said Mr Lock, who turns 81 later this year, in Mandarin.
"After that, I took up night classes in Chinese but never took the examinations either."
Instead, Mr Lock had to start work at a young age, running errands as an office boy.
During his teenage years, he illegally sold dried goods from a cart in the Tekka area. He soon decided he wanted a more stable career and got a driving licence.
The majority of his working life - from his 30s all the way until retirement at 64 - had been spent in the driver's seat of buses, taxis and lorries.
Mr Lock's jobs helped to provide for himself, his wife and four children. But he never found being a driver entirely satisfying.
"It could get very tiring and hot driving a bus," Mr Lock said. "I switched over to driving a taxi but the hours were very long, especially if you drive two shifts."
Mr Lock's work history underscores the challenges of a generation of Chinese Singaporeans who struggled with English and found job opportunities lacking.
There were many jobs he could not do, he lamented.
In 2000, Mr Lock retired when his children were financially independent - and stumbled upon the practice of traditional Chinese medicine (TCM), developing an interest in it.
But then came more obstacles.
Hoping to embark on a second career as a TCM physician, Mr Lock enrolled himself in a training course - only to find that he did not meet the minimum requirements to graduate. For example, a five-year advanced diploma course from the Singapore College of Traditional Chinese Medicine - the first step to becoming a registered TCM physician - requires at least four A-level passes.
"Due to my (lack of) qualifications, I was stuck and there was no chance to carry on," Mr Lock recalled. "I could attend classes, but I couldn't get the certificate."
Undaunted, he decided to become a specialist in traditional Chinese therapeutic massage, also known as tuina.
Yet this road, too, was closed.
Although he had obtained more than 10 TCM massage certificates, he found that he increasingly lacked the physical strength needed to be a masseur.
Following this new setback, Mr Lock set his sights on becoming a TCM pharmacist instead.
In 2007, he went back to school, taking up a full-time 41/2-year course at the Singapore College of Traditional Chinese Medicine.
In 2011, at the age of 75, he had finally found his calling.
He now volunteers at the Tzu Chi Free Clinic in Redhill, a Buddhist charitable foundation originally set up in Taiwan. Its Singapore branch provides services for those who need help, including people who need kidney dialysis or free medical services.
Twice a week, Mr Lock helps to measure out medicine dosages, check them against the patients' names and identity card numbers, and make sure that the labels match the prescriptions.
"For example, doctors can prescribe five or 10 different types of medicine, and you need to measure out the amounts and wrap them all up in one packet," Mr Lock said.
He also goes to the Tzu Chi Day Rehabilitation Centre in Jurong East three days a week to volunteer as a therapy aide.
Patients there often have difficulty moving around on their own and attend physiotherapy sessions to regain their mobility.
Mr Lock's task is to aid the physiotherapist - whether it is lifting a patient's legs or fetching the tools needed to wash his wounds.
In the past six months, Mr Lock has also gone for English classes so that he can act as a translator between Mandarin-speaking patients and the physiotherapist, who does not speak Mandarin.
"I didn't know English at all, so at first it was a bit difficult because I didn't understand. I would ask my classmates or the teacher for help," he said.
Speaking with Mr Lock, one gets the sense that he has finally found his vocation. Volunteering has mellowed him, he said.
"I've changed one hundred per cent. In the past, I had a very strong character. It was difficult for me to communicate with my wife and children," he said.
But three years after joining Tzu Chi, he began to realise that everyone's opinions on the way things should be done stem from how they look at the world.
It is this difference in opinion that often leads to strife, Mr Lock said, adding that the only way to overcome this is to set a good example and earn one another's respect.
"People tend to have a mentality that is focused on themselves," he explained. "You need to change yourself before you can change other people."