There are many examples of how glory can be tarnished. For example, a famous athlete may be caught using performance-enhancing drugs, or a politician may be caught in a scandal. In each case, the glory that the person once enjoyed is tarnished by the revelation of their wrongdoing.
The phrase "all glory is tarnished" can also be used to refer to the passage of time. Even the most beautiful things will eventually fade and decay. The glory of youth will eventually be replaced by the wrinkles and gray hair of age. The glory of a new car will eventually be replaced by the dents and scratches of everyday wear and tear.
The phrase "all glory is tarnished" is a reminder that nothing lasts forever. It is a reminder that we should enjoy the good times while they last, and that we should not be too disappointed when they come to an end.