We should “resist the natural tendency to let our attention dwell on the faults and failings of others rather than on our own”

… one of the first essentials insisted on by Bahá'u'lláh and 'Abdu'l-Bahá is that we resist the natural tendency to let our attention dwell on the faults and failings of others rather than on our own. Each of us is responsible for one life only, and that is our own. Each of us is immeasurably far from being "perfect as our heavenly father is perfect" and the task of perfecting our own life and character is one that requires all our attention, our will-power and energy. If we allow our attention and energy to be taken up in efforts to keep others right and remedy their faults, we are wasting precious time. We are like ploughmen each of whom has his team to manage and his plough to direct, and in order to keep his furrow straight he must keep his eye on his goal and concentrate on his own task. If he looks to this side and that to see how Tom and Harry are getting on and to criticize their ploughing, then his own furrow will assuredly become crooked. On no subject are the Bahá'í teachings more emphatic than on the necessity to abstain from faultfinding and backbiting while being ever eager to discover and root out our own faults and overcome our own failings…. (From a letter dated 12 May 1925 written on behalf of Shoghi Effendi to an individual believer; The Compilation of Compilations, vol. II, Living the Life)