In most cases of men taking Viagra, their problem is not a biological one. Causes of male impotency most often involve psychological issues, including things such as fear, alcohol use, performance anxiety, past relationship hurts, abuse, and a host of other things. Those who have had an instance of failure due, let's say, to fatigue or excessive alcohol intake and do not attach special significance to it rarely develop this fear. But those who elevate an occasional failure out of context and dwell on it retrospectively can go on to develop severe cases of secondary impotence.
Alcohol is probably the greatest single cause of secondary impotence.
Luckily, this isn't happening to quite the same extreme with more traditional mental disorders, such as depression or anxiety. Psychotropic medications used to treat depression, anxiety, and a host of other mental disorders are increasingly being prescribed by general practitioners and medical doctors with specialties not in psychiatry. It is drastic because the doctor is attempting to alter your brain's chemistry and absolving you of any responsibility for your feelings. To work to alter that chemical balance then would seem to be drastic, then. Yet study after study shows that people improve much more quickly with any type of medical problem or mental disorder when they take an active role in their treatment.