Yes but if a man/woman intentionally goes out to practice sex outside of marriage thinking they can repent after they've indulged in illegal pleasure, thats wrong! G-d is the most Merciful but he forgives our mistakes and after one has committed a mistake he should learn from it and never repeat.
Which is my point, Sarah. WHatever a couple does, married or not, should be between them and G-d. I don't know about you but I don't have a heaven or hell to place sinners in. I'm human just like the rest of the population. No one is perfect.
I just want to add to this discussion...there are two main types of sins: One you do against Gd and one you do against your fellow human being...Both require forgiveness.
The laws which one commits against Gd will, for the most part, be forgiven because Gd is merciful..Gd willing.
On the other hand, sin against "Man" is another story...if you hurt another person, you need to be remorseful and hopefully you'll be forgiven.
So sexual immodesty might be a sin against Gd..and perhaps yourself.
The Torah as rules and regulations and the Talmud and explanations put forth by the Rabbis are fences to prevent one from getting addicted to breaking the rules...It's not just preventing one from fornicating..it's preventing them from getting even close from doing it by, for example, not shaking hands with the opposite sex.
In as much I understand and respect these rules, what my tempt me is far less what might tempt Yaacov or Tzvi..Like I always say, "To each their own".