With her small stature, Ms Chelsea Ann Sim does not strike many as a taekwondo exponent at first glance.

The 1.5m-tall athlete also has two heart conditions that leave her breathless at times and put her at risk of heart failure.

But she has been in the sport for more than 10 years now, and has proven herself in the field, with at least four medals from major regional competitions - much to her surprise.

"I never ever imagined that this would be something that I'll continue with for so long… The medals are a privilege, not a given," she said.

Born with a hole in her heart, Ms Sim was never into sports as a child as she would get breathless if she overexerted herself.

Her worried parents took many precautions with her and she was exempted from the regular National Physical Fitness Award tests in school.

Things changed when she turned 11, as her older sister insisted that she take taekwondo lessons at a nearby community centre.

"She didn't want to go alone, so she had to drag me to go along with her. My parents decided to let us go for it since we were old enough to know our limits," said Ms Sim.

After she started, her love for the sport grew and she would beg her coach for more training sessions.

"My coach taught taiji too, and I would be at the back just practising my own taekwondo moves while everyone else around me was doing taiji."

Her coaches spotted her potential in the sport, and she was selected to be part of the national team in 2009, when she was 14 years old.

But two years later, her life was upended when her parents decided to finalise their divorce. Her father moved out of the family home - a maisonette in Hougang - where she lived with her older sister, mother and grandmother.

Her mother, who works in IT administrative support at the National University of Singapore, had to take over their housing and car loans.

"It was quite difficult for my mother as she had to handle being a single mother. And all the debts started piling up because she had to take over our loans and cope with our medical fees," said Ms Sim.

Her older sister, whom she was very close to, was also facing problems with a boyfriend, and she often had to comfort her sister.

"It was an emotional roller coaster for her as well as the rest of the family, because we had to see what she had to go through and try to help her overcome her hurdles," said Ms Sim.

She had to learn to manage these family problems, on top of a hectic training schedule - which saw her training six times a week - and her preparations for the O-level exams.

While she was close to her family who were supportive of her, there were times when she needed a break from the domestic woes.

"I felt very lost. Taekwondo became my escape; for two to three hours after school, I had this place to go to and taekwondo friends to turn to. That helped me to stop dwelling on the negative things happening at home."

To help alleviate her mother's financial burden, she applied for bursaries and scholarships, and was awarded the Singapore Olympic Foundation-Peter Lim Scholarship, which provided her with a lump sum of $3,000 to defray some training-related expenses.

She would also try to find time for her mother and sister.

"I try to compartmentalise my life, like if I know that my sister needs help, I'll just focus on being there for her and block out all other distractions," said Ms Sim.

Things eventually got better, as they learnt to cope without Ms Sim's father and her sister moved on from the relationship.

Ms Sim's training also paid off in competitions.

She bagged the silver medal for the women's individual pomsae category at the 2013 SEA Games in Myanmar.

While she was training for the 2015 SEA Games in Singapore, she was diagnosed with her second heart condition - a mitral valve prolapse that causes her blood to flow backwards into her heart.

But that did not crush her spirit, as she bettered her results at the Games, earning a gold medal in the same category.

Looking back, Ms Sim said she would not have made it, were it not for the help from her family, coaches and friends in taekwondo.

"I didn't do it alone, I am very lucky to have had a very extensive support system - from my family to the Singapore Taekwondo Federation and my coaches. They've seen me grow up through the years and groomed me to be who I am today," she said.

Her teammate, Ms Diyanah Aqidah Muhammad Dian Khudhairi, said she has always been motivated by Ms Sim, who has patiently guided her in the team.

"Even though she is small, she is someone who's strong and works very hard to achieve her dreams and goals," said Ms Diyanah, 20.

Taekwondo aside, Ms Sim works as a clients and markets executive at accounting firm Deloitte, after graduating from the Singapore Management University last year.

She also volunteers with the People's Association, where she works on community projects such as home improvement or food rationing.

Ms Sim said that over the years, she has learnt to "control the controllable and ignore the uncontrollable".

She hopes that her story will inspire others in similar situations to persevere. "It never gets easier, but it gets better."

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