You need to read the book, "Go for No". It's recommended on my 'Resources' page! I first read this book in 2007.
It taught me that No is not the opposite direction from Yes. In fact, it's on the way to it! Once I got that, my brain shifted 180 degrees. I was still fearful to talk to people as an introvert, but I lost the biggest reason for the fear. This book lays this out. Most people assume that getting a No to your offer is failure and Yes is success. That's wrong! Getting No's is a part of the process to get Yes's. If I got 1 Yes every 10 times, it meant that it took me 9 No's to get 1 Yes. Thus, No (and many of them) was on the way to Yes and success. I also learned that failure was not trying at all or giving up. This totally gave me freedom and removed a lot of my fear!
Once I got the paradigm shift, I was able to start evaluating and tracking my No's and Yes's until I knew how many No's it took me to get a Yes. As an example, I used to get 7 No's before a Yes. When I got the first No, I kept going through No and No and No. I was excited to get my Yes, but then kept tracking my No's. Over time, it took less No's to reach my Yes. Today, I get 2-3 No's before a Yes. I'm telling you! This book is a game-changer! Read it!