The Lord is slow to anger but great in power.
I was struck by this phrase in Nahum (1:3) because I'm more used to reading, "slow to anger, abounding in love." In fact a quick search for slow to anger reveals that in 8 out of 9 occurrences, all in the Old Testament, the link is with some expression of love. A few times it is even extended to include forgiveness and faithfulness.
So what's the point in Nahum then? Well it seems to me that at the very least Nahum is reminding us that God's slowness to get angry is not to be misinterpreted as either an unwillingness to discipline or a powerlessness to do so.
It's always good to remember the grace and mercy of God, but we should never forget his power to act either. He is an awesome God, a jealous God and we'd do well not to mistake slowness to anger for any lack of authority.
They say that confession is good for the soul. Well I think I'd suggest that it is only good when it is linked to disciplined choices ad actions that lead to a life that honours God and seeks to become more like Jesus. When we fail, we have God's grace and mercy on which to fall, but that doesn't mean that failure should be our default position. That we will fail is inevitable, that we don't care about our faults and failures is unacceptable.