"Definitely mental strength," he says. "Physical is important however being strong mentally gets you through the tough times including sleep deprivation, no food and the paranoia of the game play.
Last time he featured on the reality TV series, Carseldine went deep into the competition. Even then, nothing could prepare him for the psychological torment he faced during his stay on the island.
"Your mind takes you to some pretty dark places during those challenges so the key for me was to break down the challenge into small parts," he says. "It’s the only way I could get through challenges that potentially last for many hours."
And given his sizeable frame, the lack of food available also took its toll on him.
"With each day that passes it definitely gets harder as your body is searching for fuel to combat the tough living conditions," he continues.
"This is where the mental part of the game is so important. You have learn how to switch your mind off from potentially having no food for hours or a day even."
As part of his training to get in shape for the stint, Carseldine turned to high-intensity training that incorporated a range of moves that were relevant to the obstacles he'd face.
"I knew that performing in the challenges was a big part of my game so I trained pretty hard for this season with a mix of CrossFit, boxing and running," he explains.
Now, after competing twice in the show, Carseldine has some sage advice for other potential contenders.
"I think the biggest psychological trick for me was not to be someone I wasn’t. I knew that if I stuck true to myself as long as I could, other tribe members would want to play the game with me," he says.
"Be prepared for highest of highs and the absolute lowest of lows. Go in with an idea of a game plan but you have to be prepared to constantly adapt as the game moves so quickly. Regardless of how long you last in the game, the experience is a life changing one that will stay with you for the rest of your life."