Keeping your feelings bottled up and letting your worries run rampant through your brain is very damaging to your overall health. Personally, I worry about stuff that really isn't important. Maybe you feel exhausted all the time, even after a solid amount of sleep. Maybe you're eating more, or eating less. Severe anxiety needs to be treated by a qualified physician.
Untreated stress can cause a variety of physical and mental ailments.
I have found that therapy is very beneficial in controlling anxiety problems. The best combo, in my opinion, is therapy plus medications. If any of my previous statements sound familiar, please contact your doctor. Now, for my thoughts on panic attacks. I can now speak on this subject because I have experienced one.