A fear of an attack returning can cause the development of other phobias, such as performance anxiety, claustrophobia or the fear of the outdoors.       "I've talked to people who won't go to the dentist or go get their hair cut because they don't want to have a panic attack in a place where they cannot easily flee," says Margaret Summy, a Fort Worth therapist.       Often, those people assume their fear is of the dentist or of the hairstylist.       "That's not it," Summy says. "After the first attack, they start analyzing it and say, 'I'm not going to do that again.' "       One West Texas woman whom Vinson treated had refused to leave her house without her husband for 11 years, so fearful was she that another panic attack would occur.       She told Vinson that one day she left the house by herself and tried to spark another panic attack.       "You can't have one when you want to," he told her. "You have to fear it or it won't appear."      The woman has since left the house by herself.       One of the most common things sufferers say about panic attacks is: "It came out of the blue."       "It doesn't come out of the blue," Vinson says.       Often, people don't recognize the degree of anxiety that they live with daily. Left untended, it can lurk below the surface until finally we notice a physiological effect of the stress, such as a heightened heart rate. Then the fear starts.       People suffering panic attacks often visit emergency rooms and eventually undergo thousands of dollars worth of tests before realizing that their heart is not the problem.          Therapists focus on other behavioral changes, including ones that are simple and effective.          "In general, when a panic attack is coming on, the best thing to do is slow down," says Vinson. "Walk more slowly, talk more slowly, breathe more slowly."       Breath control is key in the therapy provided by Summy.       "People who have panic attacks hold their breath and are not aware of it," Summy says.           That lack of smooth breathing is associated with anxiety.       "Imagine what would happen if someone threw a rattlesnake in a room. Now imagine that in slow motion. The first thing people do is quit breathing."       It is during that gasp, that breathless moment, that people decide to fight or flee.          Even when the rattlesnake isn't in the room, we subtly reinforce fight-or-flight instincts when we do not breathe smoothly, Summy says.       Treatment begins that simply, and few would argue that the electroshock of two decades past is a better way to go.