A soul takes an oath that is seemingly redundant, to be a Tzaddik and not a Rasha. Now why take a promise that we can probably not fulfil? Instead, it is a strong mandate that we must forever strive to achieve. At the same time, even If I do not achieve being a Tzaddik, I must strive to at the very least not be a Rasha. Still, what is the purpose of taking an oath of something that I can never fulfill? The difference of a tzaddik and beinoni is the natural repelling/ feeling of repulse of evil. This is something we can train ourselves to imitate. Try to create a love of Hashem, as if you were a Tzaddik.