As a Greek I feel proud that we passed through all history tides during our high times: multiple cycles of thriving and decline, the last one being the Classical century of 5th BC, then the Hellenistic period of Alexander until we passed the baton of civilization to the Romans.
This lasted for a full thousand years until a little before Jesus birth and it continued in Europe and the rest of the world in the same way for two more until today.
It seems the reasons of decline were most often the boring ones: variable scale fightings and climate change. Any resemblance to modern times is not coincidental.
"we passed the baton of civilization to the Romans"
As a tongue-in-the-cheek retort, if the Greeks were really doing that (i.e. only playing ball in the grand building up of civilization), then the Roman Empire wouldn't ended up speaking Greek and looking so different in the period in which it is nowadays being called "Byzantine". Romans revered various Greek aspects, and somehow that privileged status that (everything) Greek enjoyed inside the empire played a role into the movement of the empire's capital to the Greek city of Byzantium (renamed Constantinople). It surely feels more like taking (the reigns, and not doing much afterwards, other than holding out for as long as possible).
This lasted for a full thousand years until a little before Jesus birth and it continued in Europe and the rest of the world in the same way for two more until today.
It seems the reasons of decline were most often the boring ones: variable scale fightings and climate change. Any resemblance to modern times is not coincidental.