"They come, an’ they quit an’ go on; an’every damn one of ‘em’s got a little piece of land in his head. An’ never a Goddamn one of ‘em ever gets it."
I didn't mean to...
When George and Lennie were talking to the bus, George had to talk for Lennie to prevent Lennie from saying the wrong things. This shows that Lennie is powerless without George to take care of him.
When Crooks was talking about the men that came to the ranch looking for money because they wanted land but didn't succeed, it showed the powerlessness of men, because they may be unable to get what they need or want.
When Lennie killed Curley's wife, he was then powerless to the fate which befell him: inevitable and soon death.