St Isaac the Syrian: When you want to direct someone toward the good...

When you want to direct someone toward the good, first put him at peace bodily and honor him with words of love. 

For nothing inclines such a man to shame and induces him to cast of his vice and be changed for the better as do bodily goods and honor, which he sees in you. 

Then, with love tell him a word or two, and do not be inflamed with anger toward him. Do not let him see any cause of enmity toward you. For love does not know how to lose its temper.

St Isaac the Syrian