This topic will only be of relevance to laypersons who are not yet willing or able to keep complete and utter celibacy. As laypersons, complete and utter celibacy is not required of us. It is ok for us to engage in sex life, so long as it conforms to the restrictions given in the suttas, which most decent people would agree with anyway (partner should be of correct age, not already with another, etc).
I have noticed in myself and other Buddhists, a kind of underlying assumption that sex pleasure is inherently 'bad' or 'unwholesome'. In my case, I got this neurotic notion from earlier Christian conditioning, and not from Buddhism, but I must say that Buddhist ideas about sex did not do much to overturn it. It is only recently that I realized that I have been mistaken for many, many years. Sex is not bad or sinful. It's just another aspect of Nature, just like eating and sleeping. Sex is how Nature replicates itself, that's all. Neither bad nor good, but morally neutral.
I put this topic here in the wellness' topic because along with my letting go of beating myself up for having perfectly natural and understandable desires in the course of having this physical human body, comes the understanding of how much harm I did to myself previously, by feeling a sense of failure every time I would 'give in' to sex desires. The guilt and shame around sex must be a great cause of mental and emotional illness in society, because it creates a terrible conflict in the average person of not ever being able to live up to their 'ideals'. (Until one reaches anagami - which is a very lofty and faraway goal, however!)
Where sex can be harmful, as I now understand it, is in the loss of life-force with every ejaculation of a man. There are literally millions of sperm cells thrown out of the body per ejaculation, and the body imbues the semen with the life-force needed to start a new life. This is why we can feel depleted and tired if we ejaculate too much. But there is actually a way to engage in sex pleasure without this loss of energy. It is by drawing that energy upwards, instead of letting it flow out of the loins. Most men conflate orgasm with ejaculation, but they are actually not one and the same thing. It is possible to have orgasm without losing any semen. There are exercizes that can be learned whereby, at the moment of orgasm, the orgasmic energy is channeled upwards,
flowing up the back and ultimately to the brain, then down again through the front of the body, in what is called the 'Microcosmic Orbit'. I believe that this art should be learned by any layperson who is still sexually active, so that they can stop the terrible wastage and depletion of energy (chi, life-force, prana) and recirculate it into their own bodies, to the benefit of health. I cannot see how it would contravene any law of dhamma to do so.