Anxiety cannot increase forever and you cannot experience peak levels of anxiety forever. Physiologically there is a point at which our anxiety cannot become any higher and our bodies will not maintain that peak level of anxiety indefinitely. At that point, there is nowhere for anxiety to go but down. It is uncomfortable to reach that peak but it is important to remember this anxiety will even out and then go down with time.
People with panic attacks often report a fear of dying or heart attack, flashing vision, faintness or nausea, numbness throughout the body, heavy breathing and hyperventilation, or loss of body control. Some people also suffer from tunnel vision, mostly due to blood flow leaving the head to more critical parts of the body in defense. These feelings may provoke a strong urge to escape or flee the place where the attack began (a consequence of the "fight-or-flight response", in which the hormone causing this response is released in significant amounts). This response floods the body with hormones, particularly epinephrine (adrenaline), which aid it in defending against harm.
Most people have experienced fleeting symptoms associated with anxiety disorders at some point in their life. Such feelings — such as having a shortness of breath, feeling your heart pounding for no apparent reason, experiencing dizziness or tunnel vision — usually pass as quickly as they come and don’t readily return. But when they do return time and time again, that can be a sign that the fleeting feelings of anxiety have turned into an anxiety disorder.
Although anxiety is often accompanied by physical symptoms, such as a racing heart or knots in your stomach, what differentiates a panic attack from other anxiety symptoms is the intensity and duration of the symptoms. Panic attacks typically reach their peak level of intensity in 10 minutes or less and then begin to subside. Due to the intensity of the symptoms and their tendency to mimic those of heart disease, thyroid problems, breathing disorders, and other illnesses, people with panic disorder often make many visits to emergency rooms or doctors' offices, convinced they have a life-threatening issue.
In order to manage threatening situations, humans have evolved to experience a "fight or flight" response. As part of this response, when humans are confronted with a dangerous situation, their body mobilizes by sending blood away from their extremities (e.g. hands and feet) and into the major muscles, producing adrenaline, and increasing heart rate so that we are better equipped to fight off danger.
Selective mutism: A somewhat rare disorder associated with anxiety is selective mutism. Selective mutism occurs when people fail to speak in specific social situations despite having normal language skills. Selective mutism usually occurs before the age of 5 and is often associated with extreme shyness, fear of social embarrassment, compulsive traits, withdrawal, clinging behavior, and temper tantrums. People diagnosed with selective mutism are often also diagnosed with other anxiety disorders.