A very stressful or intense situation, or performance anxiety, could definitely make a man lose his erection. The pressure to perform could be psychologically too intense to keep a strong one. Another, lesser talked about erection killer is difficulty penetrating a partner during sex. It’s related to performance anxiety and stress, but also fatigue. If sex becomes tiring, fatigue will bring a quick end to an otherwise great night.
Does nitric oxide help sexually?
"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.