That abstinence from food is not of itself sufficient for preservation of bodily and mental purity.
In order to preserve the mind and body in a perfect condition abstinence from food is not alone sufficient: unless the other virtues of the mind as well are joined to it. And so humility must first be learned by the virtue of obedience, and grinding toil and bodily exhaustion. The possession of money must not only be avoided, but the desire for it must be utterly rooted out. For it is not enough not to possess it—a thing which comes to many as a matter of necessity: but we ought, if by chance it is offered, not even to admit the wish to have it. The madness of anger should be controlled; the downcast look of dejection be overcome; vainglory should be despised, the disdainfulness of pride trampled under foot, and the shifting and wandering thoughts of the mind restrained by continual recollection of God. And the slippery wanderings of our heart should be brought back again to the contemplation of God as often as our crafty enemy, in his endeavour to lead away the mind a captive from this consideration, creeps into the innermost recesses of the heart.
Source: Institutes (New Advent)