The Catcher in the Rye is in many way the sad story of Holden Caulfield trying to deal with the trauma of his brother Allie's death as well as the demands that come with being near the cusp of adulthood. Holden struggles deeply with relating to other people and with himself, but along the way, he experiences moments of happiness.
For example, he meets two nuns in a diner while he is having breakfast in New York City. He donates ten dollars to them, a significant sum in that time period, and they all three start talking about Romeo and Juliet. At the end of the conversation, the nuns say they enjoyed it, and Holden says he did as well, adding as a comment to the reader: "I meant it, too."
Holden also is happy to be able to see Phoebe when he sneaks into his parents' apartment. Although they quarrel about him flunking out of Pencey and being, to Phoebe's mind, too negative, we also see the genuine affection they share. They dance together, and he gives her his hunting cap, one his favorite items.
Holden is happy too when he watches Phoebe on the carrousel in the rain:
I felt so damn happy, if you want to know the truth. I don't know why. It was just that she looked so damn nice, the way she kept going around and around, in her blue coat and all. God, I wish you could've been there.
For all that he still has many problems to work through at the end of the book, he has fond memories of the people he has described, suggesting that while they gave him pain, they were also part of his maturation process:
I sort of miss everybody I told about. Even old Stradlater and Ackley, for instance. I think I even miss that goddam Maurice. It's funny.