The march of Providence is so slow and our desires so impatient; the work of progress so immense and our means of aiding it so feeble; the life of humanity is so long, 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.
You don't realize your story is changing you until you look back.
Historians are not scientists. They cannot (and should not even trying to) establish universal laws of social or political "physics" with reliable predictive powers. Why? Because there is no possibility of repeating the single, multi-millennium experiment that constant to the past. The sample size of human history is one.