The former thought her world was over, but Finn made her realize that others are in far worse position and must adjust by appreciating everything else in life they are good at. He did this by introducing Rachel to a boy that got paralyzed playing football.
Puck, meanwhile, aimed to recapture his coolness by dating Mercedes because she's so popular now. This worked, as the nerds once again were intimidated by Puck - but Mercedes didn't love the position in which she was placed and eventually quit the Cheerios to remain true to herself.
Meanwhile, Kurt actually tried to act straight (and hook up with Brittany!) because he thought it would help him connect with his father. But Ms. Hummel gave him a great speech about also remaining true to who he is and the two of them will work through it all together. That was the central message on the show:
Love yourself, love those around you. We're all struggling with similar issues, as the closing number of "One" hammered home.
Source: TV Fanatic