"
So, I'm gonna live my life like it's my last damn night
When the clock strikes twelve, we're all gonna go to hell
What the speaker is trying to say is that she's going to live her life to the fullest and not let anyone get in her way. When the speaker says "When the clock strikes twelve, we're all going to hell," I think that what she is trying to say is that when the day dies down, you will, through your mind, go to hell.