The 27-year-old's unbeaten record appeared at risk when he was floored heavily in the sixth round of their world heavyweight title fight in April.
Klitschko continued his disciplined assault, despite Joshua's vulnerable state, and the Londoner believes he demonstrated his inner toughness while stopping 'Dr Steelhammer' in the 11th round.
"He's very intelligent, he's got a PhD, but you ain't got that hustle like me," Joshua told Sky Sports in the exclusive 'AJ - History In The Making', which you can watch at 10pm, Tuesday, on Sky Sports Main Event.
"As soon as the fight was stopped, I smiled. I said to myself 'you can't out hustle me'."
Joshua hit the canvas for the first time in his career and admits Klitschko's 'sweet' right hand completely took him by surprise.
"It was a big shot, but it wasn't enough to keep me down," said Joshua. "It put me down, it didn't keep me down.
"The shots that I feel are just when I'm being lazy. With him, I didn't even see it coming. It was a sweet shot."
Joshua reveals more in a show that looks back on a historic night in front of 90,000 fans at Wembley Stadium. The heavyweight hero is honest and open as he reflects on when the Klitschko fight was announced, what they knock down did to him and of course, the 27-year-old wonders what lies ahead...