The following hadith moved me deeply when I read it, and I should not be surprised if it has the same effect upon you. Ahmad, Abu Ya’la, Al-Bazzar, and At-Tabaraani all related the following:
"Leaning on a cane, an old man came to the Prophet (bpuh) and said, ‘O’ Messenger of Allah, I have perpetrated treacherous and wicked deeds. Will I be forgiven?’ The Messenger of Allah said, ‘Do you bear witness that none has the right to be worshipped except Allah and that Muhammad is the Messenger of Allah?’ The man said, ‘Yes, O’ Messenger of Allah.’ The Prophet said: ‘Verily, Allah has forgiven you for your treacherous and wicked deeds.’ The man departed and said, ‘Allah is the Greatest, Allah is the Greatest.’"
There are certain conclusions, or facts if you will, that one should take away from this hadith. One of them is the vastness of Allah’s Mercy. Another is that accepting Islam or making repentance wipes out past sins. Yet another is this: mountains of sins are nothing compared to the forgiveness of the One Who knows everything. And finally, it is imperative for you to have a good opinion of your Lord along with being hopeful of His comprehensive generosity and His far-reaching mercy.