We are not to live presumptuous lives, trampling under foot the blood of the covenant. We do this when we make light of sin, thinking, perhaps even before we commit sins, that the gracious and merciful Lord will forgive us. He is most gracious and merciful. He is long-suffering and quick to forgive and such characteristics should call us to love and serve Him ever more faithfully.
But if His kindness and graciousness tempt you to take advantage of Him, then you are not growing in His grace and mercy. In fact, it is just the opposite. You are growing cold and eventually His mercy towards you will also grow cold.
It is true that the Lord is patient and quick to forgive but it is also true that there is a limit to His patience. We see this time and again in Scripture in both the Old and New Testaments. When there is continual, willful rebellion, the Lord will eventually act in judgment. And the way to get to continual, willful rebellion is through tolerating and justifying your small acts of sin on a daily basis. Eventually, the heart grows cold and indifferent and festers into full-blown and open rebellion. So, what must we do to be saved? Repent of sins and seek the power of the Holy Spirit to walk in newness of life through Jesus.