This is a brilliant quote to help us treat one another more decently. It is from John Watson who was a minister in the Presbyterian Church of England who later became an author who toured North America with a short tour of fame. He died in 1907 and this quote comes towards the end of his pastoral ministry in 1904.
We must not therefore assume that our kind of religion, and our traditional views, and our favorite notions, and our particular set make the whole round world. This man beside us also has a had fight with an unfavouring world, with strong temptations, with doubts and fears, with wounds of the past which have skinned over, but which are smart when they are touched. It is a fact, however surprising. And when this occurs to us we are moved to deal kindly with him, to bid him be of good cheer, to let him understand that we are also fighting a battle; we are bound not to irritate him, nor press hardly upon him nor help his lower self. We must feel as a brother towards the man beside us, and say to him the things that we should like to have said to us, and treat him as we desire to be treated when our hands as hanging down and our hearts are heavy. This is the very essence of courtesy. – John Watson D.D. (1903), “The Homely Virtues” Hodder & Stoughton: London. pp. 168-169.