I'm game - You're saying you're in. You're not backing out. You're not

You're saying you're in. You're not backing out. You're not being a baby about it. You're just going to do it.

"I'm game," he said, even though he didn't know what was coming.

"I'm game," she said, even though she was scared.

"I'm game," he said, even though he was tired.