...FWIW, my native Finland was the only losing nation to actually pay its WWII reparations. Rather than being a cause for resentment and anger, it's just about the only thing we remember the victors fondly for: the national myth tells that by producing stuff for the USSR, we not only re-established but actually for the first time established an industrial base that subsequently gave us true international competitiveness. (It's mostly bollocks, of course, but it sounds good.)
Cardassia might remain a proud nation even when deprived of colonial holdings, as long as they have things to remain proud of. And they have an excellent and experienced propaganda machine to create such things, out of whole cloth if need be... (Or out of tatters, as it rather may be.)
First, I did not know this about Finland! Wow, unfair.
Second, I actually agree with you on the Cardassia thing. Taking some colonies away is one thing, stripping them of resources and breaking up their fleet, or dividing their entire territory (as has been suggested), are quite different matters.