Some libertines have seen an excuse in this commandment to allow themselves premarital sex and indeed sex outside of the marital institution. However, even Mosaic law makes clear that cases of rape (including with beginning consent and with minors) do not go outside this institution. For in some cases those involved were bound to marriage.
What kind of logic is this that reasons one is allowed all freedom before marriage (and why not then indeed any form of sex outside of the marriage)? What do you think the marriage institution is meant for among other things? To withold true joy and happiness from you, or at any rate some short lived pleasure? Is it not the safest place for the channeling of the sex urge! And who are the victims again? Women, girls and children; for they are called upon to go along with this dishonoring emancipation.
Some have exaggerated this commandment and they claim that marriage is indissoluable. But through repeated whoredom a marriage can be broken even in God's eyes. For even though in Romans 7. 2 it is stated that a wife is bound to her husband as long as he lives, the Lord does include a clause for divorce in Matthew 19. 9 "except in the case of whoremongering (porneia, i.e. multiple adultery, not just a one nightstand!)". That this clause does not refer to unfaithfulness during a prenuptial engagement, might be inferred from the fact that the Lord recognized the 5 previous marriages of the Samaritan woman in John 4; whereas He did not recognize the union with her 6th husband! (Notice that He did not state that "the one you have now is also not your husband"). Moreover there is the case of Paul himself in 1 Corinthians 9. 5, who defended his right to remarry when there had been brothers that disclaimed him this right! It is very plausible that he was divorced and that his wife had rejected him for another. (It was customary for Pharisees to learn an occupation and then to marry at 18).
Some go even further in their exaggerations. So Tertullian, a church father in early Christendom, preached against remarriage even after one's partner had deceased. (The apostle Paul also advises that if one is released from a woman not to seek another, but Tertullian went further than that, omitting apparently the advise that it is better to (re)marry than to burn with desire). Some Mormons go beyond this even and claim a marriage bond that lasts into eternity.
I] In committing fornication (any form of sex outside of marriage) or adultery, you play your own god in setting up your own rules. The bible calls sin lawlessness. When we go against God we are lawless.
II] You turn sex into an idol. God is Love, not sex.
III] You desecrate the holy Name of God Who made sex the crown of marriage.
IV] On what was to be the 'sabbath' of your salvation, you elevate the dirtiest work as the rest of pleasure.
V] You are disobedient to true parenthood (to what you were meant to be).
VI] You harm or even murder your neighbor's emotions.
VIII] You steal the sex that belongs to another.
IX] You lie about the truth of true relationships.
X] You put your coveting into practice. The Apostle James puts it this way: "But every person is tempted through his own desire, being drawn out and baited. Then, desire having conceived brings forth sin and sin having been completed bears death." [James 1.14,15]