Roman Catechism

Among all sacred mysteries given by our Lord as instruments of divine grace, none compares to the Most Holy Eucharist. No sin carries a heavier punishment than the unholy, irreligious, or sacrilegious misuse of this most holy sacrament, which contains the very altar and source of all holiness.
All sins must be atoned for. The sufferings in Purgatory include exclusion from the immediate presence of God and other great pains. Hence, the Church prays, “Grant rest to the souls of the faithful departed,” and the perpetual light by coffins or graves signifies our prayer for their admittance to God’s sight.