As the nervous system of autonomic response, the erection can result in different stimuli that include the sexual arousal and stimulation which is not even under the control of the conscious mind. The absence of the nocturnal erection is also used commonly for distinguishing between the psychological and physical cause of impotence and erectile dysfunction.
"Stress and anxiety can adversely affect sexual performance and are common causes of erectile dysfunction,” warns Feloney. “Feelings of stress and anxiety can also lead to depression and a loss of interest in sex." It's important to get these feelings out in the open where you can deal with them. Issues that can lead to erectile dysfunction include fear from previous bad experiences with sex, family or work related stress, poor communication with your partner, and unrealistic goals and expectations.