The actor – who plays Irish-American boxer Micky Ward in the drama – said that despite funding issues, he had faith that the movie would one day make it to the big screen.
He told Men's Health: 'It was tough. Going out and making another movie and still continuing to train for something that may not happen is not an easy thing to do.
'We're shooting 12 to 14 hours a day on one movie and I'm getting up two hours earlier than normal so I can train.
'I was so desperate to make it that I would've made any version of the movie.'
And after four and a half years of training, Wahlberg admitted that he celebrated by feasting on cookies.