The tone at the end of Chapter 7 is intense, on account of the violence of the car crash, and that intensity continues with the characters' reactions. Gatsby is left worrying about Daisy from the end of Chapter 7, continuing into Chapter 8. At the beginning of Chapter 8, the tone is set by Nick's restless sleep and anxious thoughts:
I couldn’t sleep all night; a fog-horn was groaning incessantly on the Sound, and I tossed half-sick between grotesque reality and savage, frightening dreams.
There is also the sense that Gatsby is now hopelessly clinging to his dream of getting back together with Daisy. Even the descriptions of his house suggest the end of the entire Gatsby project:
There was an inexplicable amount of dust everywhere, and the rooms were musty, as though they hadn’t been aired for many days. I found the humidor on an unfamiliar table, with two stale, dry cigarettes inside. Throwing open the French windows of the drawing-room, we sat smoking out into the darkness.
In this chapter, Gatsby relates his real story to Nick, the story of how he became Gatsby. At this point, Gatsby can only experience his dream of Daisy in memory. At Wilson's place, Michaelis tries to console Wilson after having lost his wife. The tone is intense and suggests irrecoverable loss: Wilson's happiness and Gatsby's dream. The intensity and irrecoverable loss will lead to the desperate act which concludes the chapter.
In Chapter 7 there is a jarring tone shift and a break in the flow of time. This sharp break in time is represented by the car crash.
In Chapter 8 Nick is so jarred by the death of Mrs. Wilson and the callous way Tom acts that he does not sleep well. When he hears a taxi travel up Gatsby's drive, he rushes over to warn Gatsby to go away for a while. "It's pretty certain they'll trace your car," Nick tells Gatsby, but he thinks he has some chance still with Daisy, so he does not heed Nick's warning.
He was clutching at some last hope and I couldn't bear to shake him free.
The narrative then takes on a moribund tone as Gatsby seems to recognize the end of his beautiful dream of regaining Daisy. He relates his true history and how he met and fell in love with Daisy, his relationship with Dan Cody, and his dream of becoming rich so that he could win Daisy back.
Chapter 8 is a chapter of death. There is the death of the dream of having Daisy, the death of the dream of material wealth, and the death of the American Dream as Gatsby and Wilson die.