“There are many people who often make a good Communion and who will have the benefits of this in their souls, and in eternal life, supposing that by the grace of God they do not die in mortal sin; but yet they never know the outpourings of love and the innumerable graces that can come through the Blessed Sacrament.
This is because their approach remains superficial and they pass through life encumbered with very many daily venial sins. Their lives are apathetic and graceless, they are empty, unresponsive, cold and hindered by these many great obstacles.
What are these various obstacles which do them such indescribable harm, robbing them of their share in this precious treasure whose riches fill heaven and earth, and leaving them empty and aimless, as we can see every day in so many people? Notice this well: these obstacles are our daily venial sins, cooling the love of God which should glow in our hearts, distracting our love, driving out and hindering all our devotion, taking from us and chasing away all holy consolation, making God an unknown stranger to us.
Such sins, even if they do not kill all grace in us, do all this harm nevertheless; and though they are only venial sins in themselves, they make us apt, ready and inclined to lose grace and to fall into mortal sin.”
(From Spiritual Conferences by Johann Tauler, O.P.)