The 23-year-old was devastated after France's defeat to Germany in the World Cup quarter-final while Mathieu Valbuena admitted his side were not efficient enough
The Real Sociedad winger was a frustrated figure in attack for Didier Deschamps' side as Mats Hummels' first-half goal proved to be enough to condemn les Bleus to a World Cup exit.
And Griezmann, who was visibly devastated after the final whistle, concedes the loss is the most difficult he has had to contend with.
"This is the biggest disappointment of my career," he told RTL.
"I was proud to be here, it was dream but we have a Euro (European Championship) to prepare.
"I was told not to cry and to keep my head up high. Now it's time for vacation and rest."
Mathieu Valbuena shared in his team-mate's disappointment and admits the more efficient and experienced side earned their victory on the day.
"It's a shame because we did some wonderful things," he told TF1.
"[Germany] have acquired a taste for victory. We lacked efficiency, and they had success. It's difficult to accept that it is over.
"We wanted to go through, so we are disappointed. We gave our all, but it was not enough."