St. Macarius of Corinth | The Christian receives great benefit from the Divine Mysteries...

The Christian receives great benefit from the Divine Mysteries, both in his soul and in his body. Before he communes, he must make the necessary preparation, that is, he must confess to his spiritual father, correct himself, feel compunction, acquire inner attention, guard himself from passionate thoughts as far as possible, and also from every other vice. 

Similarly, he must exercise self-restraint, pray, be inwardly awake, become more devout, and do every other kind of good deed, reflecting what awesome King he is about to receive within himself; especially if he considers that the grace which is given to him from Communion is proportionate to his preparation. 

It is evident that the more one makes such preparation, the more benefit he receives.

St. Macarius of Corinth