From Spiritual Directions of Diadochus of Photiki

Grieve only if you have committed a sin, but even in this case do not grieve too much, otherwise you may become desperate.

Those who are not capable of sinning are said that they have attained freedom. The knowledge of the Truth raises them even more. This makes them both free and above this world. But only Love creates. He who became free thanks to knowledge, because of Love remains a slave of those who have not managed to attain the Freedom of knowledge yet. He brings the knowledge to them and this develops the latter because it calls them to the Freedom. Love takes nothing: how can it take something? Everything belongs to it. It does not say, "This is mine! And this is mine!" But it says: "This is yours!"

This purity is attained through conquering the passions.

If you want to conquer lust for wealth, love selflessness and sparing way of life. If you want to conquer anger, develop meekness and generosity. Grieve only if you have committed a sin, but even in this case do not grieve too much, otherwise you may become desperate. If you want to conquer conceit, do not desire praise, laurels, nice garments, respect, favor, but like to be blamed and slandered by people... If you want to conquer pride, do not say that your deed was done by your hands and might; say that with God's help and guidance it was done, not by my power and efforts.

The acme of love is to enhance your friendly attitude to those who insult and revile you.

From Spiritual Directions of Diadochus of Photiki