In any successful therapy, you need to pick one problem and eliminate it before moving onto the next. CBT has helped me to narrow things down from an impossible morass of problems, to a small number of specific issues, which in turn allowed us to find out what is really causing these specific issues.

When you are targeting one area, you must make a conscious decision to put your other problems on the back burner. So if you have health anxiety, social anxiety and a debilitating fear of flying, you would have to choose ONE of those problems and work at it until it's either eliminated or manageable. You would pick the one that's having the most immediate impact on your life. (In this example, a fear of flying would be related to health anxiety, since health anxiety is the fear of death and so is fear of flying. That illustrates how coping with one problem can remove others.)

This is why CBT can take so long. You don't cure GAD or health anxiety in three sessions.