In my family's history, we apparently had some well-off - if not rich - ancestors. Certain people in my extended family would keep talking about these prominent ancestors. They would imply that because these ancestors were great, so were we, and so would our descendants be.
I, like others in my extended family, however, know this is bullshit. Who harps on about their extended family's glorious past like that? The answer: losers - people who couldn't point to their present or future for glory. They only had the past - one they obviously didn't even have a hand in creating.
Now, take that idea, and blow it up from a family, to an entire group of people - a nation or a race.
Who harps on about their group's glorious past, to the exclusion of the present and the future? The same answer: losers, who can only point to the past for their glory, not the present or future.
Another way to think of this is to think of glory as a stock on the market. The same rules apply:
1) Past performance does not guarantee future results.
2) What drives real glory, like the price of a stock, is its future potential.
So, to anyone harping on about their group's glorious past, to the exclusion of the present and future - you're a loser.