Our Heavenly Father saw fit to give us, his spirit children, joy. In our premortal existance (supported in Jeremiah 1:5), He ordained a plan in which we, his spirit children, could advance by coming to earth and receiving physical bodies. For us to have joy, we needed to come to earth and receive bodies. (2 Nephi 2:25)
As His spirit children, He gives us a plan by which we may return to him. We must prove ourselves worthy--not to Him, but to ourselves. He already knows how we will do. If we truly love Him, we will keep his commandments. (John 14:15)
In our day, there is more temptation than ever before. It is more difficult to keep our hands clean and our hearts pure. We are constantly bombarded with immorality from every direction. It destroys the family, which is central to Heavenly Father's plan for us to return to him. (1 Corinthians 11:11)
The bodies we posses are not ours. Jesus Christ bought us with a price--His atonment, death, and resurrection. "Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body. What? know ye not that your body is a temple of the Holy Ghost which is in you, which ye have of God, and ye are not your own? For ye are bought with a price: therefore glorify God in your body, and in your spirit, which are God's." (See 1 Corinthians 6:13-20)
He, even God, the greatest of all, taught us by example, suffered more than any mortal man could, for us, and even suffered death for us.
Through him death lost its sting. (1 Corinthians 15:55) Man may be resurrected because of Christ. All have immortality through him. Eternal life is also available unto all who take upon them the name of Christ and follow in his very footsteps. Baptism is the way we "put on Christ." It is what Christ asks of us. (Galations 3:27)
When we put on Christ, we make a covenant to keep his commandments. We covenant to love Christ and to follow him.
"Whosoever looketh on a women to lust after her hath already committed adultry in his heart." (Matthew 5:28)
You do not have to be married to commit adultry. Pornography is one of the most vile and dangerous things there is. It is as deadly to your spirit as posion is to your body. When a person fantisizes about such things he has done those things "already in his heart." It is as if he has not just looked at or read something, but as if he has participated in it. Alma taught his son that sexual sins are next to murder in seriousness. (Alma 39:5)
The power of procreation, probably Heavenly Father's greatest gift to us, is to be used only between man and women as husband and wife. Using them in other ways may bring a spirit into the world in bad circumstances outside of a family unit. Children are entitled to be born into a home where there is a father and a mother who both honor their marital vows completely. Because this can bring souls into the world before their times, it is nearly as serious as murder--a sin that takes souls out of the world before their time.
We make many mistakes. No matter how hard we try, we will never be perfect in this life. No unlcean thing can enter the Kingdom of God. (1 Nephi 10:21; 1 Corinthians 3:5-6) It took a perfect Being to pay for our sin so we can return clean. Jesus Christ, the Promised Messiah, did that. He, the very Eternal God, paid for out sins. His mercy is open to all. (Alma 32:22; 34:16) Repentance is available to everyone. It is never too late to change things. Christ stands with open arms to receive you and I. Let us not procrastinate the day of our repentance. (Alma 34:32-34) May we come unto Christ and cast off the natural man, (Mosiah 3:19) and then put on the whole armour of God. (Ephisians 6:10-18) Do this and there will be no temptation you cannot overcome. (1 Corinthians 10:13) Jesus Christ is with you. If we will draw near to him, he will draw near to us. (Doctrine and Covenants 88:63) "Return unto me, and I will return unto you, saith the LORD of Hosts." (Malachi 3:7)