“You have no one co-signing your fantasy,’’ Damon says. “It is kind of like when you were a kid making a game up in your room. It’s entirely dependent on not cracking. It was the challenge of the movie and kind of why I wanted to do it.’’
I don't have a grasp of the phrase "It's entirely dependent on not cracking"
I looked up the meaning of cracking in the dictionary but I couldn't find the relevant one.