1. Every saint has a past, and every sinner has a future.
2. Hilal bin Umaiyya accused his wife of illegal sexual intercourse and came to the Prophet (pbuh) to bear witness (against her), (taking the oath of Lian). The Prophet (pbuh) was saying, "Allah knows that either of you is a liar. Will anyone of you repent (to Allah)?" Then the lady got up and gave her witness.
[Sahih al-Bukhari 5307]
3. Jannah was created for sinners who repent.
4. "The adulterer is not a believer while he is committing adultery, and the thief is not a believer while he is stealing, but there is a chance for repentance; (if he repents, Allah will accept the repentance)."
5. "Tell the believing men to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts, etc.). That is purer for them. Verily, Allah is All-Aware of what they do."