"I was thinking about a great issue of Stan Lee’s Spider-Man comic book where he gets the flu. And he, for a time, is really weak. It was so human to me, I thought it was great. This superhero’s got the bug that affects all of us, and just like we all have to go to work when we’re sick and we really don’t know why we’re doing this and how we’re gonna do our job, he had to fight criminals when he had the flu. I thought that was incredibly human, a humanizing thing to have happened to a superhero. It was a combination of that and a desire to put that into the picture so we could identify with him. I thought that was a unique thing that happened in Stan Lee’s comics, But also there was another issue of Stan Lee’s comics that I loved where he decided to throw the suit away. It was issue number 50, perhaps, his life problems had just become too great, so I think what happened was there was a synthesis of those two ideas, along with other elements I was interested in telling in this story. That’s where the genesis of the loss of powers came from."
January 1, 1970
https://en.wikiquote.org/wiki/Spider-Man_2