I like the comparison of the Holy Eucharist to our daily food. This explains why we need the One on a regular basis, how we are healed from our venial sins by partaking of the Eucharist, finally why any grave sin can prevent Eucharistic graces from their enriching activity on human body and soul.
All of above-mentioned points are so obvious when we regard them in a context of the heavenly banquet. For only guest who ate with some kind of regularity before, can be seen as the strong and happy one during the said banquet, and then food given makes such person even stronger. Yet the mortal sin of any sort can separate invited guests from their heavenly Host since no dead man can be profitable either from any form of nourishment or from fatherly hug.
Saint Juliana of Liège pray for us!