For Catholics, Holy Days of Obligation are our most important feast days. They are the principal liturgical feasts that honor the mysteries of the Lord, the Virgin Mary, and the saints. The best way to celebrate them is to attend and participate in Mass.  Canon 1247 states:  "On Sunday and other holy days of obligation, the faithful are obliged to participate in the Mass.  Moreover, they are to abstain from those works and affairs which hinder the worship of the Lord's day or the suitable relaxation of mind and body."