It is a day to offer up our sufferings and bind them with Christ for the benefit of the souls in purgatory. No suffering is every wasted.
"The celebration of general intercession on 2 November was first established by St. Odilo of Cluny(11th century). This day is principally observed in the Catholic Church, although some churches of the Anglican Communion and the Old Catholic Churches also celebrate it. The Eastern Orthodox churches observe several All Souls' Days during the year....the Western tradition identifies the general custom of praying for the dead with the Jewish practice of prayer for the dead dating as far back as 2 Maccabees 12:42-46." ~ Wiki