The fact that the end is near makes some people want to live for the moment. Explain how Moira fits into this pattern in On the Beach.
If living for the moment means acting as if there is no future and just having fun in the present, Moira does not really fit the pattern at all. She may be like this a bit at the start of the book but, over the course of the story, Moira comes to act more as if there were going to be a future for all of them.
At the start of the book, Moira is a drunk. This fits in with the idea of living for the moment. However, she stops drinking so much. She starts to go to church. She takes secretarial classes. She goes to a lot of trouble to find a pogo stick for Dwight Towers' daughter who is not even alive anymore. By doing things like this, Moira seems to be living as if she had a future. If she were living for the moment, she would surely not spend time doing things like taking classes and she would not bother to "better herself" by cutting down on her drinking.
So Moira does not live for the moment in the way we usually think of this -- she does not become wild and crazy and hedonistic.