All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
You must continue to strive against yourself to stay away from that sin and make the fear of Allah the Almighty your provision. Be diligent to be among the youth whom Allah loves and elevates in status due to their distance from indulging in forbidden desires. It is mentioned in a hadeeth from the Prophet that he said: “Indeed Allah is greatly pleased with a youth who has no inclination towards indulging in desires.” [Ahmad, Abu Ya’la, and Al-Tabarani, and Al-Haythami said in Majma’ al-Zawaa’id: Its chain of transmission is Good.] Al-Munawi commented in At-Tayseer:
“‘Verily, Allah is greatly pleased with a youth,’ meaning He elevates their status in His sight and rewards them abundantly because they have 'no inclination towards indulging in desires'. This signifies their commendable habit of inclining towards goodness and the strength of their determination to stay away from evil. This is the state of youth, which is presumed to be the opposite of that.”
Ibn Rajab in his commentary on Saheeh al-Bukhari, said: “And in some reports, Allah says: ‘O young man who abandons his desires, who expends his youth for My sake, you are to Me like some of My angels.’” So, continue fasting, for it weakens desire.
Allah knows best.