Why is it mandatory to avoid illicit sex?

It takes the essence of sixty drops of blood to make one drop of semen; furthermore, much subtle life energy (prana) is lost in sex life.

Then there is the danger of sexually transmitted diseases, which are extremely painful and nasty.

Illicit sex causes unwanted pregnancy , sexually transmitted diseases like syphilis , gonorrhoea.

To keep women for sex life , one has to beg ,borrow,steal and commit many abominable activities which causes one to suffer a lot.

What means Illicit sex?
Any illicit sex activity ( sex outside of marriage and other than that for producing children , for example masturbation or any type of recreational sex for pleasure only ) is bad. Even sex inside marriage but only for recreation or pleasure comes under illicit sex.

The Vedic texts are the oldest manual known to mankind. Thus one cannot disregard the Vedic texts. Examples are available , which demonstrate that , what has been mentioned in the Vedic texts , is now been proved by scientists of NASA ( USA ).

For example , recently NASA Recorded the Voice of Sun. So all Scientist were shocked because it is a Sound of "ॐ" OM...!!!! This has already been mentioned in the Vedas long ago.

The Vedic Scripture tells "You have got this human form of life after many, many millions of years waiting." So do not misuse it. That is Vedic civilization, not to misuse the human form of life. Nature's law is very, very strict. This life, it is given, a chance. Nature gives a chance. Now you get this human form of life, advanced consciousness. Now you make further improvement. That is wanted. From here we can make further improvement." - SB 11.9.29 Purport

The Vedic literature indicates that , to the extent that a person becomes interested in sex, that much he loses all good qualities. For from lust develop all other bad qualities such as greed, personal ambition, hatred, and cruelty. “Sex life is the background of material existence. Demons are very fond of sex life. The more one is freed from the desire for sex, the more he is promoted to the level of the demigods; the more one is inclined to enjoy sex, the more he is degraded to the level of demonic life.” (SB 3.20.23)

Sex binds one to bodily consciousness and thus distances one from realizing one's real self within the body. For every pleasure which one derives from illicit sex , one risks equal amount of pain or suffering in future.

How to avoid trouble arising from sex?

It is been proved by medical research that to overcome illicit sex desire , Mantra meditation helps amazingly well. Mantra meditation means simply to chant the Holy Names of God with "love and devotion". You may chant any Names of God Who you have faith in. But the key is to chant sincerely with Love and Devotion , in the mood of giving and service. This has been validated by all bonafide sources ( from Vedas , Bible ) and it works. Try it. You have nothing to lose except your anxiety and bad habit.