"They were careless people, Tom and Daisy - they smashed up things and creatures and then retreated back to their money or their vast carelessness, or whatever it was that kept them together, and let other people clean up the mess they had made. . . ."
Tom and Daisy lived a life of carelessness. They were careless with their own relationship, their money, and had no mind to how they treated others. Daisy played with Gatsby's affections, all while knowing she'd never leave her husband; Tom used Myrtle and couldn't have cared less how his actions affected her husband, whom he knew and liked. Jordan didn't care about anything or anyone, she was selfish and self-serving. Gatsby could only think about his own dreams; he had tunnel vision, and Nick...... he carelessly follows the lead of those around him. Thankfully, he figures it all out.