He who busies himself with the sins of others, or judges his brother on suspicion, has not yet even begun to repent or to examine himself so as to discover his own sins, which are truly heavier than a great lump of lead; nor does he know why a man becomes heavyhearted when he loves vanity and chases after falsehood (cf. Ps. 4:2). That is why, like a fool who walks in darkness, he no longer attends to his own sins but lets his imagination dwell on the sins of others, whether these sins are real or merely the products of his own suspicious mind.
* This excerpt is from “The Philokalia: the Complete Text, Volume Two” translated by G.E.H. Palmer, Philip Sherrard & Met. Kallistos Ware