I am giving you why males become sexually impotent:-

Impotence may sometimes translate itself in occasional dysfunction or in a total lack of erection, due to some complex psychological and physiological factors.
Psychological causes are often at the origin of an impotence: fears, anger, frustrations, and performance anguish, are the main reasons. The psychological factor is always important, because erectile dysfunction may severely affect self-esteem, provoke anxiousness and depression, and make the problem even worse, by an interaction of psychic factors with organic ones.