What are the consequences of dreaming big in The Great Gatsby?How do these unrealistic, idealistic behaviours affect the characters and the book as...

Concerning The Great Gatsby, the
primary character guilty of unrealistic, idealistic thinking, and behavior that stems
from that thinking, is Jay Gatsby.  And his thinking is the catalyst for the action and
the reason for the novel.

Gatsby has an unrealistic and
idealistic view of Daisy and of his relationship with Daisy.  The consequences are that
he lives five years of his life with the sole purpose of winning Daisy back and
recreating the past--his past relationship with Daisy.  Everything that occurs in the
novel--the accident that claims a life, Gatsby's murder, etc., results from Gatsby's
illusions. 

The past he wants to recreate is an illusion. 
Daisy never loved him like he loved her.  She was not longingly looking back to her
relationship with Gatsby and wishing she were with him instead of with Tom.  Gatsby is
deluded.  He thinks they had something poignant and special.  But Daisy does not.  She
could love him, and possibly does in her own way when she talks of
leaving Tom for him, but she won't dismiss the last five years of her life and marriage
and announce that she never loved Tom, as Gatsby insists she do.  This shows that
Gatsby's view of their relationship is an illusion, and demonstrates that the
consequences suffered in the novel are for nothing.