My question is regarding sex before marriage.
I want to be clear that I know it is against God's Word to partake in such activities. I am 21 and have been a virgin all my life, avoiding temptations wherever I go. Last week my mates and I drank too much. By the end of the night I found myself with a girl and I ended up sleeping with this girl. This has never happened to me before as I would always avoid the situation or tell the girl that I do not have sex. I am surprised with myself that I let this happen and never felt so ashamed in my life. I have always had a close relationship with the Lord, and have been a good boy throughout college. Which brings me to my question: Will this one wrong ruin my chance to get into heaven?
All sins, including those you committed can be forgiven when a Christian repents of his sins (II Corinthians 7:10-11) and confesses his sins to God (I John 1:9). The point of "Or do you not know that the unrighteous will not inherit the kingdom of God? Do not be deceived; neither fornicators, nor idolaters, nor adulterers, nor effeminate, nor homosexuals, nor thieves, nor the covetous, nor drunkards, nor revilers, nor swindlers, will inherit the kingdom of God" (I Corinthians 6:9-10) is that you cannot expect to remain in your sins and make it to heaven. As Paul told the Corinthians in the next verse, "Such were some of you; but you were washed, but you were sanctified, but you were justified in the name of the Lord Jesus Christ and in the Spirit of our God" (I Corinthians 6:11). If you left sin to become a child of God, how can anyone think that continuing is some sins will let you into heaven?
Notice that sin did not begin with you crawling into bed with a girl. As Paul pointed out, being a drunkard will also keep you out of heaven. That is because when you are drunk you don't think clearly. "But you, brethren, are not in darkness, so that this Day should overtake you as a thief. You are all sons of light and sons of the day. We are not of the night nor of darkness. Therefore let us not sleep, as others do, but let us watch and be sober. For those who sleep, sleep at night, and those who get drunk are drunk at night. But let us who are of the day be sober, putting on the breastplate of faith and love, and as a helmet the hope of salvation. For God did not appoint us to wrath, but to obtain salvation through our Lord Jesus Christ" (I Thessalonians 5:4-9). This is also why Peter warned, "Be sober, be vigilant; because your adversary the devil walks about like a roaring lion, seeking whom he may devour" (I Peter 5:8). Because you were drunk, it wasn't hard for Satan to get you naked in bed with a girl.
All forms of drinking are to be avoided by Christians because of the spiritual dangers that can result. "Therefore, since Christ suffered for us in the flesh, arm yourselves also with the same mind, for he who has suffered in the flesh has ceased from sin, that he no longer should live the rest of his time in the flesh for the lusts of men, but for the will of God. For we have spent enough of our past lifetime in doing the will of the Gentiles -- when we walked in lewdness, lusts, drunkenness, revelries, drinking parties, and abominable idolatries" (I Peter 4:1-3). See: Old Testament Beverages and New Testament Beverages for more details.