Halle - who worked on the soundtrack for the film with her musician partner Van Hunt - added how she instantly related to the characters.
She said: "When I read this script it just grabbed me. I intrinsically understood all the characters, I understood their brokenness, I understand what it is to fight for second chances, last chances.
"I understand what it is to be a mother and try to be a working mom and how hard that can be.
"There's just so many elements to this movie that I just connected to and I couldn't let it go once I read the screenplay."
And her own love of MMA fighting made her jump at the chance to tell the story.
She added to 'Entertainment Tonight': "I just couldn't let this go and I had a great love of MMA at the time when the script came my way.
"I'd grown up being a huge fan of boxing.
"I always loved a good fight film. I love that quality of people finding redemption and forgiveness and rising above all the odds. I always feel good when I see moves like this."