From the book Ancient Art of Self Healing which is a collection of excerpts from lectures, notes and classes by SSS Harbhajan Singh Khalsa (Yogi Bhajan)
(The following information is geared towards Men)
"Righteous sex is when you are sexually right. Never indulge in sexual relationships with anybody for any reason other than to relate to the soul of the person. Don’t make a mess out of that creative energy. Eighty drops of pure blood makes one drop of semen. Eighty drops of pure semen make one ejaculated drop. If it leaves your head, mentally after that moment you are gone. If it leaves your backbone and lower back, that is, if it works from your thighs, it means your calcium, potassium and magnesium are lost. Each drop of the ejaculated semen contains all the vitamins, all the basic metals, and the basic fiber which is used for everything in the body. It is a very pretty, precious thing. If you take an average of $3.00 a meal, one ejaculation costs you $150.00 in food alone. Be sexual; we don’t mind; you can play with it as much as you like. But when you are 65, you will think about it and there will be nothing. The bottle will be empty and you can only then blow the whistle.
Sex is a wonderful thing. Attachment to it is just a trap out of which you never come out. It makes you worse than an animal. An animal is done when the spring season is there, new blood is there, energy is there. You have a spring even in the winter, When you have sex as a release, when you have sex as a communication, when you use sex for any other purpose than sex, you have lost yourself, period. Now think about your mind, and what you want to do. Sex is your sixth sense.
You must understand that when you indulge in sex, you just join your bodies together. Your aura integrates with the aura of the other person. Positivity of sexual relationship is a gift of God, and other than that it is a hell.
Some people have had sex with an older woman; some people have had sex with women of negative characteristics. That is one point of life when you are totally exposed. All your gates (chakras) can be damaged, nothing can be left in you."