I love remembering the following passage from the writings of Robert E Lee.
It was first made public by Colonel Charles Marshall in 1887, in Southern Historical Papers published in 1889.
More recently you can find it in Richard Weaver's essay on the Christian warrior, found in The Southern Tradition at Bay, pg 209.
My experience of men has neither disposed me to think worse of them, nor indisposed me to serve them; nor, in spite of failures, which I lament, of errors, which I now see and acknowledge, or, of the present state of affairs, do I despair of the future.
The march of providence is so slow, and our desires so impatient, the work of progress is so immense, and our means of aiding it so feeble, the life of humanity is so long, and that of the individual so brief, that we often see only the ebb of the advancing wave, and are thus discouraged.
It is history that teaches us to hope.
Here's a link to the Marks Collection, which distributes this fine print entitled "The Christian General".
