We'd all like to think that we've lived a good life, or a meaningful one. And although we know deep down inside whether or not we're fulfilled, it helps to look at things situationally. Are you doing good work? It's probably best to listen to people you admire and see what they think of whatever you're doing.
And while it's true that many things are based on opinion and the definition of what's "good" varies from person to person, there are some things that are just undeniably great.
Like sacrificing yourself to save others in the face of a great national tragedy? You can't really knock that. It's safe to say that if you were a hero cop on let's say, oh 9/11, you're worthy of some praise and recognition, like NYPD sergeant Timothy Roy.