Faust doesn't always do the right thing, but he does closely adhere to his initial desire; though he makes mistakes, he never loses sight that his goal is to develop and learn and grow. Faust strikes a deal with the devil knowing full well what the outcome will be, therefore he knowingly aspired to the desires of this life and ignored that path that would have found him eternal life. Regardless, he uses the devil for his own purposes. Goethe’s Faust isn't about spiritual growth it's about Faust's develpment as a person.