The novel seems to strongly and directly agree with the notion in Fitzgerald's famous quote: "There are no second acts in American lives."
Jay Gatsby certainly tries to create a second act for himself and for Daisy. By accumulating great wealth, Gatsby paves the way for a new future wherein he recaptures the past, as he explains to Nick.
Nick seems to state the obvious here, yet Gatsby insists that his ideal and his dream are attainable.
“You can’t repeat the past.”
“Can’t repeat the past?” he cried incredulously. “Why of course you can!”
We can describe Gatsby's great dream of marrying his true love - after she has already married someone else and after he has lived the life of a bootlegger - as a second act.
This dream fails dramatically, and fails first as an attempt at a second act, broken free from an earlier stage of life. Gatsby insists that Daisy tell Tom that she has never loved him. He pushes Daisy toward the future by insisting that she nullify the past.
For Daisy, this is too much to ask.
“Oh, you want too much!” she cried to Gatsby. “I love you now—isn't that enough? I can't help what's past.” She began to sob helplessly. “I did love him once—but I loved you too.”
Gatsby's hope to begin afresh is significantly hampered by his idealism in this example. By insisting on a perfect break from the past, he undermines his goal of starting on a path to a new future with Daisy.
The car accident that kills Myrtle is the next stroke against Gatsby's dreamed of second act, followed by Gatsby's death. For Daisy as well there is no second act. She goes back to Tom and the two live much as they had before.