According to Osho, 'conquering' the soul has two inseparable meanings: first, self-mastery—regaining authority over thoughts, emotions, desires, so you can rely on yourself rather than be ruled by impulses; second, self-knowledge—directly knowing your own being. For Osho, knowledge is victory: only by knowing yourself do you truly master yourself, and only with mastery can your freedom, love, and promises be trustworthy.
It means being able to steer your mind and feelings, and clearly knowing who you really are.