By showing that just because darkness returns after light had extinguished it doesn't make the previous effort wasted. In fact, quite the contrary. In our real world, the struggle to win WWI wasn't any less of a stellar achievement just because fewer than 30 years later there was another World War. Those heroes, and their sacrifices, didn't mean any less. Many of them lived to see WWII take place, and stood on as inspiration. And some of them even groomed the heroes who fought that next one.
The triumph of good over evil (in any galaxy) is like passing a baton. You just have to keep increasing the lead, and giving the next generation an easier go of it. And if you were so great that your run ends up being the most memorable, and gets the most glory, all the better.