The author starts by observing that most people are "indignant" at the idea that they might not be reliable authorities regarding what they really want. The author then argues that knowing what you really want is difficult and often requires hard work and risk. He adds that people tend to avoid this work and "unconsciously convince themselves" that they want what their society dictates for them.

This is a bit of a tricky structure for a Main Conclusion question, because the author does not directly state his main point in a separate sentence. Rather, he first states that "most people" don't like the idea that they aren't reliable authorities about their real wants, then the rest of the stimulus defends that idea — i.e., that they really aren't reliable authorities about their wants. In other words, as you read the last three sentences, you should ask yourself, "So what?": What's the point of saying that "such self-knowledge" (knowledge of one's own wants) requires hard work, and people unconsciously internalize what their society says they should want instead? The point is to support the claim that most people are not reliable authorities about what they want, even though most people don't like that idea. So we know that idea is the main point of the argument.