“…while refraining outwardly from sinful deeds, one may have an attraction for them or a delight from them in one’s heart; so also, doing righteous deeds outwardly, one’s heart may not be in them. Only true zeal both wishes to do good in all fullness and purity, and persecutes sin in its smallest forms. It seeks the good as its daily bread, and with sin it fights as with a mortal enemy.”
(St Theophane the Recluse  in ‘Path to Salvation’)