https://www.psychologytoday.com/us/blog/insight-therapy/201807/7-common-misconceptions-about-anxiety
Many people who deal with anxiety and panic will recognize the situation: you are somewhere doing something. Suddenly, your body is a frenzy of symptoms. You’re breathing hard, dizzy, and lightheaded; your heart is beating a mile a minute; you feel like you’re going crazy. Feeling your anxiety rising, you tell yourself that if you don’t do something, the symptoms will continue to escalate in a linear function, fast and upward with every passing minute, getting worse and worse ad infinitum. This prediction is intuitive, but erroneous.
In fact the relationship between panic symptoms and time is not linear but curvilinear, shaped like an inverted U. If you stay with your symptoms past the point of marked discomfort, they will continue to escalate for a while, but not forever. After a while they will level off, and then decline. This is largely due to the physiological process of habituation by which prolonged exposure to the same stimulus leads to reduction in nervous system excitation, and hence reduced anxiety.
People who deal with anxiety and panic are often uneducated about this fact. One reason for this is that they have never experienced it in real time because they tend to escape the situation before entering the habituation zone. Thus, an important part of anxiety treatment involves exposure practice, by which a person is guided to remain with their symptoms past the point of discomfort, to give their nervous system the time to habituate and to provide them with firsthand evidence refuting the linearity assumption.