Know Your Material After several years of research and several months of writing it up as a dissertation you probably know more about the topic than anyone else in the world.
Review everything anyway. Each section of the proposal meets goals critical not just to a successful proposal defense but to the success of the entire dissertation research endeavor.
However, the most important defense is the dissertation defense which comes at the end of a long and arduous process and which may have unfolded over a number of years. You should also ask your supervisor and other committee members to share with you, to the extent that they can, the areas of your work on which you should focus your preparation.
The only one still doubting is you. How to defend your PhD dissertation December 15, by T. Treat yourself with a complete new outfit.