Confidence does not come from finding the right words. Confidence comes from saying it confidently--basically, from knowing that you mean it, and that if questioned about what you mean you will have followups and answers. Basically from asserting that your version of reality is correct, in the face of others questioning it.

If you're actually confident about your version of reality, you can say it in any words you want and it will seem confident and stand up to scrutiny.