This point is important – the anticipatory anxiety.  Sports men and women regularly use “mental rehearsal” to help them prepare for a match.  They imagine the shots, the game and perform according to plan when the event arises.  Research has show that musicians mentally practicing their instrument in their mind, use the same brain processes as when playing for real.
Inside the cell, NOS catalyzes the oxidation of L-arginine to NO and L-citrulline. Endogenous blockers of this pathway have been identified. The gaseous NO that is produced acts as a neurotransmitter or paracrine messenger. Its biologic half-life is only 5 seconds. NO may act within the cell or diffuse and interact with nearby target cells. In the corpora cavernosa, NO activates guanylate cyclase, which in turn increases cyclic guanosine monophosphate (cGMP). Relaxation of vascular smooth muscles by cGMP leads to vasodilation and increased blood flow.

To start with, ED is NOT in your head. You can’t simply will yourself to get an erection, no matter how much you try. Studies show over 80% of ED cases are caused by a treatable physical disorder. Diseases such as diabetes, high blood pressure, and high cholesterol are common causes. Even a perfectly healthy man can develop ED after a brain or spinal cord injury. ED can be a side effect of certain medications, too.  Read more on our Causes of ED page.
The causes of erectile dysfunction include aging, high blood pressure, diabetes mellitus, cigarette smoking, atherosclerosis (hardening of the arteries), depression, nerve or spinal cord damage, medication side effects, alcoholism or other substance (drug) abuse, pelvic surgery including radical prostatectomy, pelvic radiation, penile/perineal/pelvic trauma such as pelvic fracture, Peyronie's disease (a disorder that causes curvature of the penis and sometimes painful erections), and low testosterone levels.
Half of all men between the ages of 40 and 70 will experience erectile dysfunction. While the problem doesn't cause heart disease, the two often occur together – study after study has shown that men with ED are dramatically more likely to develop heart disease and have a heart attack or stroke. One German study from 2010 found men with erectile dysfunction are twice as likely to die within the next two years as those without, prompting some experts to call the phenomenon "the canary in the trousers".
Picture the scene. You get home from the bar with your date. You both decided to leave a little early, after only two drinks, because the chemistry was really there and both of you wanted to cut to the chase and get intimate. To discover each other's bodies. To eat of the fruits of passion. In short, to have sex. You stick the key in the lock, swing the door open, and invite her into your beautiful place. OK, well it might not be exactly beautiful. It might be a bit of a mess, frankly. But you don't let that ruin the moment. You turn around and passionately kiss her. How the two of you make it to your bedroom with some clothing still on is anybody's guess. You jump on the bed and hurriedly strip. God — can't this go any faster, you wonder? 
Erectile dysfunction is a surprisingly common experience. It has been estimated that at least 1 in 10 men is affected to some extent yet, because of the embarrassment and even shame which has been attached to this condition, many men do not seek treatment. Growing older is a factor, with the number of those experiencing erectile dysfunction increasing with age, but it affects the entire range from the youngest to the oldest.
Qaseem, A., Snow, V., Denberg, T. D., Casey, D. E., Forciea, M. A., Owens, D. K., & Shekelle, P. (2009). Hormonal testing and pharmacologic treatment of erectile dysfunction: A clinical practice guideline from the American College of Physicians. Annals of internal medicine, 151(9), 639-649. Retrieved from http://annals.org/aim/article/745155/hormonal-testing-pharmacologic-treatment-erectile-dysfunction-clinical-practice-guideline-from
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