Common mistakes candidates make during UPSC preparation include improper time management, lack of focused study plans, and neglecting current affairs. Additionally, many aspirants underestimate the importance of the optional subject or fail to integrate regular revision into their schedules. Relying solely on subjective materials without practicing answer writing can also be detrimental. Finally, an overemphasis on theory without practical application often leads to gaps in understanding, making it imperative for candidates to strike a balance throughout their preparation journey.