What specific strategies can riders use to ensure their bike is properly prepared for a big event, and what are some key checks that should be performed in the days leading up to the race to avoid last-minute mechanical issues? Are there any particular tools or equipment that are essential to have on hand, and how can riders balance the need to make adjustments with the risk of over-tinkering and introducing new problems? Additionally, what role does bike preparation play in the overall mental preparation for a big event - can having a well-prepared bike actually help to reduce anxiety and improve performance?