I wish I had a good idea for you. I understand those doom feelings. They are mean and ruthless and make you feel very vulnerable. Exercise is excellent, so you've got that covered. What I try to remember is that my anxiety induced thoughts are causing faulty thinking. Try hard not to take these thoughts too seriously...easier said than done...and know that the feelings will pass. I try to distract myself by playing a game on my tablet or getting caught up in a tv show. Anything to interrupt the bad thoughts.