Obsessive-compulsive Disorder (OCD): In OCD, a person becomes trapped in a pattern of repetitive thoughts and behaviors that are senseless and distressing but extremely difficult to overcome. Such rituals as counting, prolonged handwashing, and repeatedly checking for danger may occupy much of the person’s time and interfere with other activities. Like panic disorder, OCD can be treated effectively with medication and/or psychotherapy.
So I can tell you that panic attacks aren't dangerous, but I recognize that this is "easy for me to say". If you're having anxiety attacks, especially if they're a relatively new occurrence for you, you might not be able to believe this right now. That's entirely understandable when you feel that your life is threatened! You don't need to take anything here on faith. Instead, check it all out. Test everything I say against your own experience, as you work your way through this site.
The combination of good self-help information and working with an experienced anxiety disorder coach, counselor, or therapist is the most effective way to address anxiety disorder and its many symptoms. Until the core causes of anxiety are addressed - the underlying factors that motivate apprehensive behavior - a struggle with anxiety disorder can return again and again. Identifying and successfully addressing anxiety's underlying factors is the best way to overcome problematic anxiety.
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).