If someone is judged worthy to receive the gift of knowledge but allows his heart to be full of bitterness or rancor or aversion to another, it is as if he had been struck in the eye by a thornbush. That is why knowledge is no good without charity.
My brother, the passions are afflictions; and so the Lord does not excommunicate us because of them, but He says: 'Call upon me in the time of affliction; and I will deliver thee, and thou shalt glorify me'. Therefore, when beset by any kind of passion, there is nothing more useful than to call upon the Name of God. All we can do, weak as we are, is to flee for refuge to the Name of Jesus. For the passions, being demons, retreat if this Name is invoked.
If we want to do something but cannot, then before God, Who knows our hearts, it is as if we have done it. This is true whether the intended action is good or bad.
A wise elder gives the following advice to monks and youth alike: 'Avoid eating foods which are to your liking, but, preferably, eat the simplest foods, and be thankful to God, Who also sends you these.'
If you have received from God the gift of knowledge, however limited, beware of neglecting charity and temperance. They are virtues which radically purify the soul from passions and so open the way of knowledge continually.
In everything we do, God looks as the aim, whether it is for Him or for some other purpose we act. So, when we wish to do something good, let us have as our aim not to please men but to please God, so as to have our eyes always fixed on Him, doing everything for Him, lest we bear the labor but lose the reward.