I’ve posted this before, but it bears repeating:
?If anybody should ask me how this communion [i.e., the true communion of the believer with the very body and blood of Christ] takes place, I am not ashamed to confess that that is a secret too lofty for either my mind to comprehend or my words to declare. And to speak more plainly, I rather experience than understand it? (Institutes of the Christian Religion, IV. 17 . 32).