It does not matter what she does, she hates coming second.
Castle (40) has played representative netball, tennis and bowls.
She won the New Zealand mixed pairs title in bowls with Mike Kernaghan in 2009.
She exudes a passion for everything she takes on.
The competitive streak was ingrained into her from a young age.
Her father, Bruce, was a former Kiwis rugby league captain and her mother, Marlene, a former World Bowls champion who has won three Commonwealth Games medals that she keeps in a drawer at home.
Raelene has reached representative level in three sports - tennis, netball and bowls.
"My parents have been great support to me, whether I was playing sport or in my business career," Castle said.
"The competitive nature to be the best at whatever you do was something they definitely taught me."
Before taking the helm at Netball New Zealand in mid-2007, Castle was head of business marketing at Telecom after holding high-ranking positions at Fuji Xerox, Southern Cross and BNZ.
She believes there are definite parallels between her commercial roles and the sporting world.
As chief executive of Netball New Zealand, Castle is in charge of the largest women's organisation in New Zealand.
"I want to be successful at my job," she said.
"We must be successful financially and on the court."
She also likes winning on the green.
"My competitive nature has been bred into me," Castle said.
"I didn't have to worry about it. It is in my genes. I like to be competitive in sport and also in my job."
Growing up in a sporting household where both her parents represented their country has turned her into a crazy sports fan.
"I absolutely love sport.
"I watch it all the time, I talk about it a lot, I engage with it and I really enjoy it," she said.
When she was young, Castle used to get up in the early hours to watch league and rugby tests on television with her father.
She still does.
The demands of her job has meant that she is not able to put as much time into bowls as she would like.
But she still harbours an ambition to represent New Zealand.
Time is on her side because Marlene Castle did not start playing bowls until she was in her mid-40s.
"I find bowls a good break away from netball," Castle said.
"I would like to win another New Zealand title.
"I'd love to emulate my mother but my job at Netball New Zealand is very big.
"Bowls must take second place to this but I'd still like to make it to another level in the sport."
She used to play a lot of bowls with her mother.
It was good mother and daughter time.
"Bowls is a special sport.
"You can play against a world champion, and perhaps beat them, and experience that special feeling.
"In no other sport can you do that," Castle said.
Her mother is a top bowls coach in Auckland and told her daughter the secret.
"It is all about low, slow and flow," Castle said.
"Success in bowls is all about consistency of delivery."
