Sabau has a nicely organized list there, and someone else certainly hit the nail on the head by saying, "You can do it" after other things you've overcome.

The oral defense can be stressful. However, you chair has no business allowing you to defend if he or she does not believe you are ready. Do you trust your chair? Have you withheld or distorted the information about your readiness? If your answers are respectively, yes and no, then you might look upon the defense as an opportunity to have a nice chat about your research with a knowledgeable team of people -- whom you chose to be your advisors -- who want you to succeed.

Your chair does not benefit one bit if you you go down in flames -- it suggests that this chair did not know how to prepare you. If you have picked people you respect as ethical people and researchers for your committee, all will be well.

Big hugs and very best wishes. Let us know how it goes.