The same way you cure all idolatry — serious, serious nagging.
Laziness is idolatry. In that sense, it is closely related to its opposite, workaholism. Both sins are sins of self-worship. The behavior looks different, but the root idolatry is the same.
And the problem is that Law cannot do what Grace does. There is no saving power in Law. And there is no sustainable abiding of the Law apart from the Grace compulsion. We can command repentance, but it’s Grace that enables repentance and belief that accompanies it. Repentance problems are belief problems.
When we are set free from the Law’s curse, we are set free to the Law’s blessings. The difference maker is the gospel and the joyful worship it creates. Any other attempt at Law-abiding is just behavior management.
So you don’t cure laziness by pouring Law on it. God turns dry bones into living, breathing, worshiping, working bodies by pouring gospel proclamation into them. When we truly behold the gospel, we can’t help but grow in Christ and with the fruit of the Spirit.
Religious people can’t delight in the law like David did. They have to be set free — and feel free — from its curse first. And people aren’t lazy because they think they’re forgiven for trespassing the Law; they’re lazy because they think the Law doesn’t apply to them.
We worship our way into sin, and we have to worship our way out. When someone is lazy (or restless) they do have a sin problem, but the sin problem is just a symptom of the deeper worship problem. Their affections are set somewhere else. And wherever our affections are set is where our behavior will go.