If Donal Walsh's life hadn't been tragically cut short by cancer, he would have celebrated his 21st birthday last week. Landmarks like these are difficult for his mother, Elma, who is reminded of all that he missed out on. "When you see his friends move on you wonder what would he be doing and what would he be like," she said.

Elma joined Brendan O'Connor on Saturday to talk about her extraordinary son and her family's life in the years since he passed away. Donal rose to national prominence in 2013 when he appeared on Brendan's Saturday night show, aged 16. With only months to live, he spoke about the worries he had for his family and regrets for what he would miss. He also pleaded with young people not to take their own lives.

"I'm here fighting for my life for the third time I've no say in anything. And I'm still here, waking up every day. And they think they have a problem and this might be a solution? That does make me angry, I'm not going to lie about it. I have nothing against people with mental illness but these people have to realise that there is help."

Donal's message resonated with the public at a time when suicide rates were alarmingly high, particularly among young men. Donal's home county of Kerry had the highest suicide rate in Ireland, with 32 people taking their own lives in 2012. He saw each death as a preventable tragedy and wanted to change attitudes. More than anything, though, he wanted to live, according to Elma.

"He said one time, 'If I could just live til I'm eighty with all the pain, if I could just live. He just so so wanted to live, but he knew that his was going to be a short life."

In the months after Donal received his terminal diagnosis, he was determined to experience as much as he could. That included drinking a pint ("It didn't really suit him," laughed Elma), and going to an over-18's club with a fake ID.

"He was 16 and asked me could he go to discos and I couldn't say no because he was going to die and I couldn't say yes because he was 16. He said, 'But Mom, I'm not going to live til I'm 18, I'm not going to see what a disco's like….so I did, I left him make the fake ID. I actually helped him."

After Donal appeared on The Brendan O'Connor show, the family were overwhelmed with cards, gifts and offers of support and help. Some of it, however, was unwelcome. When people started to send 'cures' for his cancer, Elma became annoyed and upset.

"It's not fair to get the hopes of a 16 year old boy up all the time. So while people did call to the door with different cures like aloe vera and meditation – and some could be insistent, in fairness – they were the ones I was cross with because I didn't have time. I didn't have time to explain that it is something that we didn't want because he was terminal, there was no comeback."

Thousands attended Donal's funeral in May 2013, including his sporting heroes Ronan O'Gara and Paul Galvin. Many of the town's shops closed their doors as a mark of respect. "How the town of Tralee could shut down for a 16-year-old boy was just overwhelming," Elma said.

Elma and Finnbar have set up the Donal Walsh #LiveLife Foundation in his honour, which brings them to schools all over Ireland to share his life affirming message. "We've travelled to over 120 schools since last September, and that doesn't include the walks and the cycles and the churches we go to…we have a reach of around 50,000 young people that we visit every year throughout Ireland and Northern England."

The foundation has raised over €400,000 for suicide prevention and mental health organisations so far. You can find out more about the foundation here.

You can listen back to Brendan's full interview with Elma here.