When we sin

Leviticus 5:3-5 (NLT) summarizes what we should do when we sin.

When you realize what you have done, you must admit your guilt ... When you realize its foolishness, you must admit your guilt ... When you become aware of your guilt in any of these ways, you must confess your sin.

In order to recognize our sin, it's help to return, as often as possible, to the Ten Commandments. Those serve as a guide to righteousness, and also as a mirror into our sin.

But as emphasized in the aforementioned passage from Leviticus, once we recognize our sin, we must confess, because, as David says (Psalm 66:18-19, NLT),

If I had not confessed the sin in my heart,
    the Lord would not have listened.
But God did listen!
    He paid attention to my prayer.

So these passages summarize a life of faith. We must (1) educate ourselves on what sin is, and (2) confess our sins. Doing so ensures that God will hear our prayers!