No one ever answered this question better than Titus Livius, whom we know as Livy, who wrote his History of Rome during the time of Augustus Caesar. And here is his answer.
“The study of history is the best medicine for a sick mind; for in history you have a record of the infinite variety of human experience plainly set out for all to see; and in that record you can find for yourself and your country both examples and warnings; fine things to take as models, base things, rotten through and through, to avoid.”
Any questions?