We must not rely too much upon ourselves, for grace and understanding are often lacking in us. We have but little inborn light, and this we quickly lose through negligence. Often we are not aware that we are so blind in heart. Meanwhile we do wrong, and then do worse in excusing it. At times we are moved by passion, and we think it zeal. We take others to task for small mistakes, and overlook greater ones in ourselves. We are quick enough to feel and brood over the things we suffer from others, but we think nothing of how much others suffer from us. If a man would weigh his own deeds fully and rightly, he would find little cause to pass severe judgment on others.
–Thomas à Kempis
How to refrain from harsh judgmental attitudes and thoughts toward others… take an honest look at yourself.
Doing so produces much humility in ourselves and much compassion toward others.