[Be patient, Mark, this is for you.]
Years ago, Woody Allen (whom I now boycott) made a movie entitled "ALICE" which starred Mia Farrow as a housewife who consulted a famous Chinese doctor to help her deal with certain psychological issues. (I don't know: Is boredom an issue? Or is it a state of mind? Do we care?)
Anyway (I promise not to have too many more parentheses) Dr. Yang, the Chinese doctor in the movie was drawn with mythic strokes; his herbal prescriptions seemed to have far-reaching effects on Alice, and spurred her to make changes in her life. I don't remember all of the reviews, but it they weren't glowing. It was kind of an offbeat movie. But the thing is, the character of Dr. Yang was based on a real person, not the same name, so don't get any ideas. And I got to meet him, take a couple of classes with him, see him for my own health issues, and bring a patient to him. His knowledge of Chinese medicine and herbs was, simply, staggering. His understanding of Chinese energetics, upon which herbal and acupuncture treatments are based, was brilliant to the point of elegant simplicity, the kind of simplicity you get to after so many years of study and immersion, you arrive back at the beginning; completely turned around and seeing with new/old eyes.
He was in his 80's at the time. English was not his strong suite, so I had to listen carefully. He spent a long time on my pulses, tongue and face. He made notes in Chinese and gave orders to minions. Then he gave me packets of herbs in a powdered form: Just add water, hold your nose and swallow. But they were so powerful that after just one day, my tongue and pulses completely changed. And I had several periods of free association that were so deep and far-reaching, I still refer to them for inspiration.
The problem was, they were also very expensive and after a couple of months I could not go back. But I had a wealthy patient who was willing to see him and have me accompany her to take notes and observe. The patient had a large non-cancerous growth and was trying to avoid surgery. I had tried to tell her over and over that the growth was a result of internal cold; a solid mass that accumulated because she was so depleted and kept pushing herself. But people of her ilk do not want to be told that. They just want ways around the inevitability of running out of gas.
I watched the doctor do his initial evaluation. Then he spoke:
"You are 4-cylinder car trying to go like 6-cylinder car. " Goosebumps. Just that morning my patient had revealed she had had a strange dream in which she was in a car trying to go up a hill and she could not make it and kept sliding back down.
My patient tried to explain that she had a very demanding job and that she needed more energy. She was trying to reason with him. The doctor looked at her compassionately, and in a deep and resonant voice said: "Mind has no limit. Body has limit."
That was basically the end of her entreaty. There was simply nothing she could say to that. It was an essential truth of stunning simplicity, and not at all the way we learn to think about the body-mind.
In terms of the male sexual ability to perform, this is also apt. There is not necessarily anything wrong with you if you have mental/emotional desire, but not enough energy to complete the job. You are not always supposed to be able to. The body has its way of protecting your essential energy (kidney jing) or life force -- a finite amount you are born with -- so that you do not use too much of it and compromise your health. Or age before your time. This happens in response to two basic things: Aging, which is inevitable; and a too-great demand for energy.
That said, there are certainly things one can do to optimize your response. But first you need to evaluate what's really going on. It may be your yang that is depleted, not only your yin. Or it may be both. For instance, depleted yang could leave you colder or paler than normal. You might notice your workouts are harder to complete. Depleted yin is what is responsible for hot flashes or certain heat symptoms, among other things.
Do you get enough sleep? Sleep is the great restorer of yin and yang energies. Without enough sleep, we age faster, have slower responses to immune system challenges, and don't always feel vital sexual energy, to name just a few of the many ways lack of sleep affects us. Just because caffeine can sharpen our senses and prop open our eyelids after a poor night's sleep does not mean that the rest of our bodies are following along.
The second thing to look at is: are there any underlying physical conditions that would cause your response to be compromised? Your doctor would be the one to determine this. You can also consult a practitioner of Chinese medicine for an energetic diagnosis that would take into an account any lifestyle habits that might be impacting your general health. Moxibustion, the practice of using smoldering 'moxa' -- a preparation of the herb mugwort -- on certain points is extremely beneficial for bolstering/warming up male yang energy and yin.
In short, without seeing you face-to-face, and with very little information, it would be difficult to give more than a general opinion on what you could do. The beauty of Chinese medicine is that it gives an individual a differential diagnosis based on that person's specific imbalances and often uncovers the beginning of sub-clinical conditions before they become more serious. And the treatments are also very directly addressed to a patient's body, not to the disease or condition as is common in western, allopathic medicine.
Be gentle on yourself and do not have the expectation that to be male is necessarily to be able to perform at will. To be male, is, after all, to be human.