act against one's own interests and hinder one's own advancement is correct because stand in one's own light means to harm one's own chances or progress by one's actions.

This idiom or phrase is useful because it helps students understand the intended meaning beyond the individual words.

Examples: If you refuse every opportunity, you stand in your own light. A student stands in his own light when he ignores helpful feedback.

This idiom is about hurting one's own progress, not ordinary ignorance or social embarrassment.