I'm gonna do it.
Saying 'I'm gonna do it' is like a person screaming into the void. They're going to do something absurd, and it's all because someone else told them to.
I'm gonna do it. I'm gonna eat all the cookies in the jar.
I'm gonna do it. I'm gonna text my crush 100 times.
I'm gonna do it. I'm gonna try to run a marathon in pajamas.