In offering ourselves…

If we look carefully within ourselves, we shall find that there are certain limits beyond which we refuse to go in offering ourselves to [God]. We hover around these reservations, making believe not to see them, for fear of self-reproach… The more we shrink from giving up any such reserved point, the more certain it is that it needs to be given up. If we were not fast bound by it, we should not make so many efforts to persuade ourselves that we are free.
— François Fénelon (1651-1715)

When we transcend…

But when we transcend ourselves, and become in our ascent towards God, so simple that the naked love in the height can lay hold of us, where love enfolds love, above every exercise of virtue that is, in our Origin, of Which we are spiritually born, then we cease, and we and all our selfhood die in God. And in this death we become hidden [children] of God, and find a new life within us: and that is eternal life.
–Blessed John Ruysbroeck (1293-1381)

Observe abstinence…

As long as the flesh is in full health, let us observe abstinence at all times and in every place. When it has been tamed (which I do not suppose is possible this side of the grave), then let us hide our accomplishment.
— Saint John Climacus (c. 525-606)

Do you fast…

Do you fast? Give me proof of it by your works.If you see a poor man, take pity on him.If you see a friend being honored, do not envy him. Do not let only your mouth fast, but also the eye and the ear and the feet and the hands and all the members of our bodies. Let the hands fast, by being free of avarice. Let the feet fast, by ceasing to run after sin. Let the eyes fast, by disciplining them not to glare at that which is sinful. Let the ear fast, by not listening to evil talk and gossip. Let the mouth fast from foul words and unjust criticism. For what good is it if we abstain from birds and fishes, but bite and devour our brothers?
— Saint John Chrysostom (347-407)