Question:With the Scripture: "You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart" (Matthew 5:27-28). Only married people can commit adultery, so as I see it, this Scripture is not meant for the unmarried.
What you are doing is narrowing the application so that it doesn't include your particular sin. By doing so, you show yourself to be the same breed of person as the Jews of Jesus day, "Woe to you, scribes and Pharisees, hypocrites! For you pay tithe of mint and anise and cummin, and have neglected the weightier matters of the law: justice and mercy and faith. These you ought to have done, without leaving the others undone. Blind guides, who strain out a gnat and swallow a camel!" (Matthew 23:23-24).
You missed the point of Jesus statement completely. The Jews of Jesus' day read the Law, saw that it said "Do not commit adultery," and then congratulated themselves that they did not have sex with another man's wife. Jesus' point is that sin doesn't start when a person physically does the sin, it starts when a person seriously contemplates the sin. "And He said, "What comes out of a man, that defiles a man. For from within, out of the heart of men, proceed evil thoughts, adulteries, fornications, murders, thefts, covetousness, wickedness, deceit, lewdness, an evil eye, blasphemy, pride, foolishness. All these evil things come from within and defile a man" (Mark 7:20-23). (Notice that fornication is in this list as well.) You can take any sin and make the same point. Jesus choses adultery for this particular illustration, but it also works with murder, stealing, covetousness, and fornication. A sin doesn't begin at the physical act, it begins when it is strongly desired (lust).
"Let no one say when he is tempted, "I am tempted by God"; for God cannot be tempted by evil, nor does He Himself tempt anyone. But each one is tempted when he is drawn away by his own desires and enticed. Then, when desire has conceived, it gives birth to sin; and sin, when it is full-grown, brings forth death. Do not be deceived, my beloved brethren" (James 1:13-16).