Due to the persistence of sin, you lose that Taufeeq of wanting or willing to do good Deeds, Allah takes that Taufeeq away from you, you begin to see praying, fasting and all other acts of worship as a burden to you.
We learned from the Quran and Hadith that Allah gets very pleased when we leave all our wrongdoings, repent and revert to the straight path. But then we know It's the nature of man to make mistake, but we need to make it a habit to rectify our mistakes for then we become amongst the best.