Hell, what do we define as successful? Pax Romana which arose after nearly a century of political decline and strongmanship/near warlordism? Then the crisis of the third century, the string of emperors, bashing against Parthia/Sassania again and again, the Gallic and Palymran Empires, the decay of the West due to disease, depopulation, economic struggles, a rise of brigandage, the tying of the Proto-Serf Coloni to the land to serve the Villas and Nobilies/Patricians, the Germanic/Iranic breakaway 'vassal kingdoms'? A fallback from Germania and Dacia after what - two hundred years? When Rome left Britain, the Britons immediately emerged with little presence of Romanization left over, because the Romans treated Britain like a frontier zone than a core part of the Empire. When they left Spain, the Vascones rose up almost immediately. When they left North Africa, the Romano-Moors popped up. Strong Roman presence was in Gaul, Spain, and Italy; I can say little for the Balkans as they were one of the hardest hit areas of the Western Decay from 400 onwards, depopulated and repopulated massively.
The East suffered even more of a languishing death, though from 650 to 1000; they had a pretty good Golden Age. Even the Justinian Era before that was marred by high tax, internal problems, frequent wars, mistrust, and broke after his death. Then after that it was turbulent, until the Kommenians, which fell to the Crusades, then a last spark by the Palaiologos, drawn out for almost a hundred years of being a veritable city-state until 1453, a few successors for a while after, until gone by ...1470, wholly?
I mean, sure, apropos for lasting that long, but it was one hell of a ride that doesn't scream so much success, rather, resiliency and stubbornness.