I'm 18 years old. I have lived in sin for a very long time, but I just started to seek Jesus again. I have a problem: I always lived in lust for women whether it be online or in person. There's this girl who wants to ... ughh ... commit adultery. How can I hold myself back from her? She's coming home in a week, and she wants to meet me. I always try to hold myself back, but eventually I give into lust. How can I lust no more? I don't want this anymore. I just want to live a better life.
"Keep your heart with all diligence, for out of it spring the issues of life. Put away from you a deceitful mouth, and put perverse lips far from you. Let your eyes look straight ahead, and your eyelids look right before you. Ponder the path of your feet, and let all your ways be established. Do not turn to the right or the left; remove your foot from evil" (Proverbs 4:23-27).
"Now then, my sons, listen to me and do not depart from the words of my mouth. Keep your way far from her and do not go near the door of her house" (Proverbs 5:7-8).
You speak as if you have no self-control, which cannot be true. While you desire to have sex, you don't have to give in to the desire.
What Solomon tells us is that the first step is to get control of your heart, because your desires will lead you astray if you don't guard yourself. The second step is to remain honest at all times with other people and with yourself. So often people give into sin because they tell themselves lies. They try to hide their sins by telling other people lies. The third step is to control what you look at. If you find the female form aluring, then look somewhere else (Job 31:1). Finally, you control where you go.
Therefore, if you don't want to commit adultery, you immediately stop talking to this adulteress. You don't meet up with her. In fact you find other places to go and other things to do until she is gone. Only by not starting things that you don't want to finish are you going to be able to avoid sin.
In regards to lust in general, you need to stop looking at woman as objects to have sex with. You need to see them as real people. So no more pornography. "But I say to you that everyone who looks at a woman with lust for her has already committed adultery with her in his heart" (Matthew 5:28).
In addition, you need to start filling up your life with righteous things so that you don't have time to think about sin, let alone commit sin.