Sorry if all this is a bit depressing there is one thing to hang onto. Sometimes it is just not your fault, and it didn't really matter how well you did, the odds were just stacked against you. Knowing this should help you keep things in perspective. You need to concentrate on the things that you can control - the things that you meant to say but didn't, the opportunities didn't grasp. Review every interview that you have, learn from the experience and move on.
Persistence is the key to success.