The 29-year-old Mexican, who pushed for the opportunity to be the opponent at New York's Madison Square Garden following Jarrell Miller's suspension, is convinced the time is right for him to succeed where he has previously failed.
It continues to haunt him that his only professional defeat, on points by a majority decision to Joseph Parker in 2016 for the WBO title since won by Joshua, came after he struggled to perform as he believes he can.
Although Saturday's fight represents a far great challenge, he believes th lessons learned from that defeat will ensure he capitalises on the biggest opportunity he is likely to have.
It needed not only Miller's suspension, but Ruiz Jr's recent defection from Top Rank to Al Haymon, and victory only last month over Alexander Dimitrenko, to create the circumstances required for him to be in New York this week.
Despite being offered the fight at late notice that victory also means Ruiz Jr is both confident and sharp. He said: "That's exactly how I feel. My heart, my mind, my soul. It's destiny.
"Things happen for a reason, and the reason is for me to become the first Mexican heavyweight champion of the world. (Joshua's) got all the belts and everybody's trying to fight him. He's a big money name. I'm here to conquer what he has. When I fought Parker I went all the way to his hometown (Auckland). A lot of people don't know about the training camp I had; I trained myself for that fight.
"Even though I was with (respected trainer) Abel Sanchez, he was just a little bit busy. I learned a lot from him but I've learned about working hard. Before I was slacking off too much. Now I have this opportunity, I feel amazing.
"I felt down but us fighters are warriors, we get back up, work harder, and I'm back here, getting this opportunity to make history. I come forward and throw combinations that Joshua hasn't seen. I hit harder than Jarrell Miller, and I'm faster."
Asked if that defeat could therefore make the difference on Saturday, he responded: "It sure will. Knowing what I can do, we're going to come out victorious.
"In that fight I could have done a lot more, could have thrown a lot more. The training camp we had wasn't good but I've been active so I feel amazing, loose, my condition's good, and I'm ready.
"From being with Top Rank, getting out of there and going with Al Haymon was the best thing that happened in my life. I'm willing to die in the ring to get this victory. I'll do whatever it takes to get it."
