Unbeaten champions Joshua and Parker will unify their WBA, IBF, IBO and WBO belts on April 1 (NZ time) at the Principality Stadium in Cardiff.
Joshua says one defeat should not define a fighter, but every unbeaten boxer still goes into the ring with the fear of losing.
Speaking to Sky Sports UK eight days out from the highly anticipated fight, Joshua said he is focused on the bout and is open to what a potential loss could mean for his career.
"In boxing, losing is the one thing you are nervous about," Joshua revealed to Sky Sports. "Nobody wants their '0' to go. You don't plan on getting beat - in every other sport you can lose and bounce back.
"[Roger] Federer is still known as a great, but we don't know the 10 people who have beat him before. For boxing, that loss stays on your record for eternity.
"Losing doesn't define you though; it's how you move forward that defines you. You have to know where you are going.
"When I look at heavyweight boxing, you look at [Wladimir] Klitschko, and he wanted to be a three-time heavyweight champion of the world, he lost and came back - If I lost, I'd dust myself off and go again.
"It would show people's mindset if they discredited everything I had done up until that point because of one defeat."
Asked, 'Is [losing] what scares you?' the 28-year-old heavyweight champion from Watford answered: "Yeah because it is the sport we are in."
Regardless of how the fight plays out in just over a week's time, Joshua is hopeful of putting on the gloves for at least 10 more years.
"I'm fully focused on Parker," Joshua continued. "Who's to say afterwards I couldn't fight on for another 10 years?
"I'm 28, Klitschko retired at 40 years old, and Mayweather is 41 and people say he could still fight on. Who is to say I couldn't fight on until 38? History shows athletes go on a lot longer, provided they take care of their body.
"I don't want to have to leave boxing; I want to do it because I love it. I don't want to do it for the fame, and I want to do it because I enjoy it and still want to be at a high level."
Photo by Reuters