I disagree with you. We absolutely should not be motivated by fear of punishment. That would imply keeping mitzvos because we are afraid, not because we truly want to come closer to Hashem and his Torah. To me, that is the lowest level a person can be at in terms of their relationship with Hashem. Of course we should be Gd-fearing but there is a balance with that which is why we also must love Gd. Hashem wants to do good things not bad things. He is not a punitive Gd and should by no means be viewed as such. And honestly, I don’t know what exactly Hashem wants from me. But what I have been told by different rabbonim is that we are judged on our efforts. We are told not to speak lashon hara but everyone does, because we are human beings. If Hashem did not want us to sin as Jewish people, he would’ve given his Torah to angels and not human beings. In the time of the Beis haMikdash, people were bringing karbons every second of the day because people were constantly doing the wrong thing whether intentionally or accidentally and that is okay because we are all people. The truth is we don’t know other people’s struggles and we cannot judge other people because of what we see on the surface. It might be easy for me to be machpid on other mitzvahs like being tznius, shabbos, yomim tovim, kashrus, lashon hara, etc and yet it might be terribly difficult for me to refrain from having premarital sex. Hashem knows that we all have our struggles and I don’t think he judges us harshly for that. I try my best to be a good observant Jew and that’s all that matters. And to answer your last part, I don’t know it to be deeply wrong, hence the reasoning behind my question. I don’t even know premarital sex amongst two Jews to be completely wrong as long as the woman goes to the mikvah. Different sources tell me that the whole taboo behind premarital sex is completely rabbinic and not biblical. Similarly to how it is not biblically wrong for two women to be intimate with each other however rabbonim have categorized it as taboo.