Argentina's challenge was ended by Mario Gotze's effort in extra time, and Mascherano admits that he will always feel pain after coming agonisingly close to clinching the trophy.
"The pain is immense," the Barcelona midfielder told reporters at the Maracana. "We gave what we could and we are sorry for ourselves and the people.
"The sadness is for life."
Argentina have not lifted the World Cup since 1986 in Mexico.