Be holy, for holy am I, the Lord your God (Lev. 19:2) - this is a commandment from the Old Testament, all the more obligatory for us, who are already living in the times of new grace. And indeed, becoming like one’s Lord is the natural path of every believing soul who loves God and strives to overcome the sin that lives in it. However, evil sometimes seems omnipotent, and holiness seems unattainable and accessible only to selected people who have achieved perfection in spiritual life—saints. This book explores whether it is possible to keep the commandment to be holy in the modern world.