Weiss admitted that there are no "emergency plans" in place in case the HBO series is suddenly cancelled, as their aim is to retell George R R Martin's book series as extensively as possible.
"We realise if it all goes well, it could potentially be quite a long commitment," he told The Huffington Post.
"We'd read the books, same as anyone, and we had spoken to George about where things were going, and we went in with eyes open, knowing that if all went well, we would end up with a very, very long, coherent story that spanned several seasons of television."
He added: "It's always seemed like an all-or-nothing, damn-the-torpedoes kind of enterprise. It's something that you're either going to do right or you're not going to do at all.
"So to the best of our ability, we're going to keep trying to do it right and not make any emergency/contingency plans because I don't think fear is going to help make the show be what it should be."
Weiss also said that making such a commitment to Game of Thrones had given him "confidence" to stray from the source material.
"Sometimes it's a confidence to violate the letter of the books to do better service to the spirit of the books, which is something we did in the first season," he said.
"It really is about the show finding its own legs. I do think it really is about just being willing to take the risks that are necessary to do justice to the show as a show."
Game of Thrones was officially renewed for a third season last week.
Season two currently airs Sundays at 9pm on HBO in the US and Mondays at 9pm on Sky Atlantic.
> 'Game of Thrones': George R R Martin hints at season three