Imam Hasan al-Basri rahimahullah was once asked: "Shouldn't one of us feel too shy to ask his Lord to forgive his sin, then do it again, then ask for forgiveness, then do it again?"

The Imam said: "The Shaytaan wishes that you would have this attitude, so do not tire of asking for forgiveness."

 
[al-Jami al-'Uloom 1/165]