Having a clear conscience is essential to serving the Lord effectively. There are many traps that people can fall into whereby their conscience becomes tainted unnecessarily.
Eternal life doesn't mean eternal time, but rather, living outside the constraints of time itself. Don't let being time-poor rob you of being effective for God.
There is a tendency for some to consider themselves victims. In God's kingdom you should take responsibility for your own actions, instead of acting as a victim of your own failings, or the failings of others.
Through the death and resurrection of Christ, God was able to give us a new covenant. We have both mercy and grace in this covenant, making it superior to the Law. The mercy God offered David is the same that God offers today.