Vicente del Bosque's world champions suffered the ignominy of a 5-1 hammering in their Group B opener on Friday, as the Netherlands gained a measure of revenge for their final defeat to the Spaniards in 2010.
Doubles from Robin van Persie and Arjen Robben were complemented by Stefan de Vrij's header as Louis van Gaal's side responded superbly after Xabi Alonso's penalty had put the holders ahead.
And Iniesta, who struck the winner in the final four years ago, insists he and his team-mates will try to learn from their humbling.
"We have to win the two games that are left. There are small details that tip the balance. But it was difficult for us," said the Barcelona playmaker.
"We are prepared for whatever comes. We'll do our work, but we won't forget about this."
For a philosophical Del Bosque, days of contemplation await ahead of Spain's all-important clash with Chile on Wednesday.
"That's sport," he said.
"We have to accept defeat. They were better than us in the second half.
"We have to admit that they were better. It's a delicate moment for us, but we have to solve it."
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