People don't learn, they never freaking learn.
The under-dog polis of Thebes gains fluke power for a decade or so between the Battles of Leuctra and Mantinea and manages to blow it by a series of bad diplomatic maneuovers and rotten luck.
But as soon as they get a democratic government, every city with a different constitution becomes unenlightnened potential enemies who must be "shown the light". So ditching their best general (the man with the catchy monicker Epaminandos), the big-wigs send the army round deposing oligarchs and setting up democracies. With a heavy death toll in the resulting instability and often no change whatsoever to the actual constitution of the polis - then the moment their self-righteous backs are turned, some tyrant springs up to fill in the vaccuum.
Then the deposed oligarchs do a round-up, defect to Sparta and reclaim their cities. Now strongly anti-Thebes.
By this stage, no polis has retained a powerful, or even peaceful, position for more than 14 years at a stretch since the Archaic period when they first began to cement political identities and many states have lost up to half their citizen population!
Don't even get me started on the Romans.
And this is a good day - I'm up to speed on work, no restaurant until Friday, Pagan stuff is sorted out and I feel almost peachy. But history really gets my blood boiling.