The loss in New York was the first of Joshua's 23-fight professional career and he has dismissed suggestions anything was wrong with him.
"I had no panic attack," the 29-year-old said in video posted online on Wednesday.
"I have to take my loss like a man. No blaming anyone or anything."
Joshua's promoter Eddie Hearn announced on Tuesday that a rematch with United States-born Mexican Ruiz, part of the contract for Saturday's fight, would take place in November or December.
"I am the one who went in there to perform and my performance did not go to plan. My gameplan didn't go to plan," added Joshua.
"I have to readjust, analyse, do my best to correct it - and get the job done in the rematch."
The Briton was floored four times as Ruiz won in seven rounds at Madison Square Garden.
Before the final round, Joshua looked perplexed in his corner and said to his trainer Rob McCracken: "Why am I feeling like this?"
The London 2012 Olympic champion subsequently had a concussion test.
Joshua says his pre-fight training camp in Miami was "spot on" and he did not eat any contaminated foods. He also said he would continue to work with McCracken.
"There have been a lot of accusations and worries about what was wrong with me," he added.
"I want to tell you this: I am a soldier and I have to take my ups and my downs - and on Saturday I took a loss.
"Congratulations to Andy Ruiz. He has six months or so to be champion because the belts go in the air and he has to defend them.
"I would not mind if [the rematch] was in New York again or in England."