* The dangers of excessive drinking: Nick is describing the social scene at Gatsby's parties, where alcohol flows freely and many attendees become intoxicated. He sees the potential for trouble and danger in this excessive consumption, particularly in the context of the wealthy, often reckless, and morally loose people attending.
* Nick's moral compass: This statement underscores Nick's moral clarity and his sense of moderation. He's not judgmental, but he recognizes the dangers of excess and the importance of maintaining control. This makes him a stark contrast to many of the characters surrounding him, particularly Gatsby himself.
* Observational perspective: Nick's role as the observer allows him to comment on the lives of others, particularly Gatsby. He can see the potential dangers Gatsby is courting by surrounding himself with such a crowd and by attempting to win Daisy back through extravagant displays of wealth.
* Foreshadowing: This quote foreshadows the potential for tragedy. The excesses of Gatsby's world and the moral recklessness of his party-goers ultimately lead to tragedy, both for Gatsby himself and for other characters involved.
Essentially, Nick's observation highlights the destructive power of excessive drinking and the benefits of maintaining one's moral compass and sense of self in a world that is often consumed by excess and recklessness.