Laziness is easy.  It does not require any effort or thought.  However, unoccupied hands and undisciplined minds invite Satan to tempt us to wickedness (Ephesians 4:25-28).  It was apparently a problem in Crete where laziness was part of the national character (Titus 1:12) and therefore Paul instructed that the new Christians should learn a new way of life allowing no space for Satan to work.  At the same time, by doing what was good and right, they would earn their own living, provide for their families, and be good examples to the church.

In the same way that uncultivated agricultural land loses its nutrients over a period of time, so that it is useless in the long term, so Christians who do not discipline themselves to do good each day cannot serve the interests of God's Kingdom.  Indeed the devil will take advantage of their idleness (1 Peter 5:8).   

But we cannot simply serve from instruction and discipline, we also need encouragement – from the Lord Jesus (2 Thessalonians 2:16) and the love of the fellowship (Philemon 1:7).  Paul's letter to Titus therefore concludes with greetings from his ministry team as well - they all wanted the new believers to be useful to God.  And Paul especially wanted to encourage those he had led to Christ; it was important that they should not slip back into old ways (1 Peter 1:14).

Changing our hearts to want a new lifestyle is only possible through God's grace.  He takes the initiative to reach out to us.  As we respond, He fills us with His Holy Spirit giving us spiritual gifts to enable us to work productively in His Kingdom.  For most of us, that productive work takes place in the context of our employment, enabling us to be a blessing to our families and local communities.  Our workplace is therefore more than just a source of personal revenue, but part of God's purpose.  He knows that work is good for us, however hard it may be.  And as we work, embracing the challenges, He is at work inside us, to change us to be more like Him and to strengthen us so that our lives will not be unproductive.