Norman Crowley employed eight people in his welding company before he turned 18.
By the age of 40, he had founded and exited three businesses, including Inspired Gaming Group, which sold for $500m in 2008. He currently runs Crowley Carbon, Crowley Solar and Electrifi.
As a serial entrepreneur, Crowley has learned a thing or two about building resilience - something that comes inevitably in the high-risk, hard-knocks life of a start-up.
Getting tough isn't just a question of taking it on the chin, he says. It's also about knowing how to look after yourself.
"When people say 'you're a seasoned entrepreneur', what they really mean is that you've had the shit kicked out of you so many times that you've become quite resilient. But you learn a lot from something going wrong and the subsequent problems that happen.
"For example, the government's announcement that they're going to shut down Ireland for six weeks starts a whole list of stuff that needs to be sorted: you have people that are stuck abroad who need to come home, you have people with childcare issues, you've got deals that you thought were going to close that aren't going to close now.
"You learn how to manage your own emotions, that it's not all about money, how to pick up the pieces when it all falls apart. That is the journey of the entrepreneur, these massive highs and massive lows.
"To pick yourself up from the lows and grind it out you have to go through a callusing of the mind - it just gets used to trauma, threats and challenges.
"When there's something threatening happening, you can't be a good leader if you're exhausted or you've drunk too much coffee. So if you want to run a serious organisation, you have to be physically capable of running that organisation, as well as mentally.
"I meditate every single day, and I journal. It helps you to get comfortable in your own skin. If you can meditate, exercise and eat properly every day, these are highly tangible things that you can do to ensure that you are fit for doing the role that you're supposed to be doing. Because it's not easy."
Image credit: Unicorn PR