Courtesy

This man beside us also has a hard fight with an unfavouring world, with strong temptations, with doubts and fears, with wounds of the past which have skinned over, but which 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.

Simpler version:

Be pitiful, for every man is fighting a hard battle

Colloquial version:

Be Kind; Everyone You Meet is Fighting a Hard Battle