thesis committee - My PhD defense is next week and I am having negative thoughts about my work and knowledge. Any advice on how to tackle this?

I am presenting my PhD thesis in front of my committee next week and I feel that I have just not done enough. My work is simple and I also feel that I have poor theoretical foundations and am going to be an embarrassment when quizzed by my committee.

I am not feeling confident about presenting my research and I am finding it extremely difficult pushing away negative thoughts like (I feel I have not done enough or I am not theoretically strong enough for doing my PhD on my research field).

I am revising theoretical stuff (related to my thesis work) that I studied in my first year of PhD, but I am not able to push out the feeling of guilt and the impending doom.

Any advice on how to tackle this?