This quote is from the book “The Catcher in the Rye” by J.D. Salinger. Holden Caulfield, is annoyed by people, especially a psychoanalyst, who keep asking him if he’s going to try hard in school when he goes back next September.
A lot of people, especially this one psychoanalyst guy they have here, keeps asking me if I’m going to apply myself when I go back to school next September. It’s such a stupid question, in my opinion. I mean how do you know what you’re going to do till you do it? The answer is, you don’t. I think I am, but how do I know? I swear it’s a stupid question. (p. 234)
Holden thinks the question is dumb because he believes you can’t really know what you’re going to do until you actually do it. He says it’s a stupid question because life is unpredictable, and people can’t predict their own actions. Holden doesn’t like being pressured about his future plans, and he thinks that questions like these oversimplify the complexities of life and personal choices.