Don't be afraid to ask questions, it's how you will learn. Request bi-weekly meetings with your advisor at some point after candidacy. This is necessary to make sure you get started on a productive topic. Finally, if you decide that you've made a mistake and that you can't work with your advisor, proceed decisively but carefully. NOT wait too long to confront the issue.
Confidence level is at a high point.
When you begin your graduate degrees, you are confident but intimidated. You have just finished your undergraduate degree, have been accepted by a first rate institution, and are not sure whether or not you can make it. You pass your candidacy exam and are on top of the world, brilliant, can conquer any problem. It dips drastically. You are trying to define your Ph.D. topic and probably hit one of many low points.