do you think people set unrealistic goals?

In general it depends on the people. I think most everybody yearns for what the characters in Steinbeck's novella seek. We want to belong, we want to be accepted and we want to be loved. Some people attach all kinds of conditions to this which can make the goal unrealistic. An example might be, "I want to belong as long as you agree with everything I say." In "Mice and Men" perhaps the goal of a simple farm was unrealistic given human nature and Lennie's very limited sense of social-interaction.