He/she will help you learn to cope with the anxiety/panic, and find ways to dismiss the intrusive thoughts
. I know it's very scary, but I can reassure you that anxiety will not harm you.
Another thing you can do is to get some exercise, eat healthy, try to get sufficient sleep, and keep yourself distracted. Get busy with life...work, school, hobbies. The less idle time you have, the less catastrophic thinking you will do.