Thomas A Kempis 1.14 - Judging others is reckless

Judging others is reckless

Look out for what you are doing yourself, and watch out that you are not judging what others do. In judging others a man's efforts are blocked, often wrong, and generally sinful. Turn to yourself for judging and critiquing, and that effort always brings a good result. As things seem to our heart, so we judge them; we easily lose true judgment because of our own personal feeling. If God were always the pure object of our desire, we would not be so easily troubled by the resistance of our feelings. 

There is always some secret thought within us, or even joining it from without, that pulls us off course. Many secretly seek their own goals in things, without realizing it. They seem to have good peace of mind so long as things go the way they want. But because of different feelings and opinions, there often arise disagreements between friends, between countrymen, between religious and godly men.

An old custom is difficult to let go, and no one is easily led to see beyond themselves. If your own reason is your greatest resource or your own efforts, more so than the strength of being under Jesus Christ, you will rarely be an enlightened person, because God's will is for us to be wholly under him and to transcend all reason through a burning love. 

Imitation of Christ by Thomas A Kempis, 1.14. 

Translation focused on contemporary English and preservation of rhetorical force and art

(I haven't forgotten section 1.13, but it is particularly long and will need to wait for another day.)