Iniesta, 26, settled Sunday's World Cup final with an extra-time strike against the Netherlands.
And his goal sparked mass celebrations in Spain, with millions partying in Madrid and Barcelona.
"It's hard to explain," he said when asked how his decider made him feel.
"All I can say is that I feel very happy, and to have scored such an important goal for everybody, to make millions of people happy - that is priceless.
"A lot of people follow us and suffer with the national team, so to see them all so happy is priceless."
Iniesta also expanded on his decision to dedicate the win to Dani Jarque, the Espanyol captain who died of a heart attack in training last year.
"It's always been in my mind to pay tribute to him in some way," Iniesta said.
"He was a footballer and the idea came about before the final. Fernando Llorente mentioned it to me because some of our team-mates were doing similar things.
"And what a moment to pay tribute to such a great person and great friend like Dani. It was the best tribute in the best moment to make sure he remained with us."