In the beginning of chapter 3, Slim and George sit down together talking about Lennie. Slim notices the oddity of two men traveling together in the words:
Hardly none of the guys ever travel together. I hardly never seen two guys travel together. You know how the hards are, they just come in and het their bunk and work a month, and then they quit and go out alone. Never seem to give a damn about nobody.
This shows how typical lonliness was in that era for migrant workers.
Next, we see how dreams gave hope to several characters, not just George and Lennie, but also Curley's wife who can't let go of her past dream of being in the movies:
Coulda been in the movies, an' had nice clothes - all them nice clothes like they wear... Because this guy said I was a natural." (84)
She talks about this in chapter 5 just after Lennie killed the puppy, but before he hurts her. It's interesting on this same page, Lennie refers to his dream shortly after hearing her finish hers.
Crooks noted the prejudice of his early days by recollecting,
There wasn't another colored family for miles around. And now there ani't a colored man on this ranch an' there's jus' one family in Soledad. If I say something, why it's just a nigger sayin' it. (67)
Crooks feels lesser and worthless. He demonstrates this as he feels outnumbered and that he has few people with whom he can identify.
In the book Of Mice and Men the theme of loneliness is evidenced in the book by Candy who clings to his dog even though the dog is old and smelly and should be put down. When the group of hands decide to put down Candy's dog, Candy struggles for a reason to keep him alive.
"Candy looked for help from face to face." (45)
As for dreams, George and Lennie hold onto their dream by telling the story of their dream over and over again. Lennie frequently asks George to tell him about the dream.
""Well, it's ten acres," said George. "Got a little win mill."
The negro hand had to sleep away from the others because he was black and not allowed in with the others. He was a stable buck and a cripple. Lennie went to Crooks doorway and spoke to him. He asked Crooks innocently why he wasn't wanted.
"Cause I'm black. They play cards in there, but I can't play because I'm black."(68)