Maxine is on an emotional rollercoaster after leaving the scene of her affair.
Though she expected to feel guilt, all she felt in this moment was excitement, as she sped down the interstate with one hand on the steering wheel, and the other in precarious places. The energy she feels is intoxicating, so she knows she won't be falling asleep any time soon.
She has a wild night, full of exhibitionism as she pulls up to a 24-hour fast food joint to give the man at he window a "show", before getting the cops called on her. Suddenly, the guilt hits her like a ton of bricks, so she drives to her fiance's house to make it up to him.