Myopia (short-sightedness) is the inability to focus the eye on distant objects.  Peter uses it as an illustration of those Christians who have received so much from God (grace, peace, faith, promises and power - 2 Peter 1:1-4), and yet are unwilling to put everything into their relationship with Jesus.  That is why Peter has prescribed a spiritual work-out of: practising goodness, getting to know God, self-control, perseverance, godliness, kindness and love (2 Peter 1:5-7).

Then he describes the reason why some believers refuse to work-out for Christ's sake.  They simply do not see any reason to change their lifestyle.  The problem is not that they cannot see the future (although they cannot), but that they cannot see the past.  They have forgotten all that the Lord Jesus Christ has previously done for them.  They may have once gladly heard and received the gospel, but when they forget the enormity of their sins and the greatness of their salvation, there is no motivation for active lifestyle change (Titus 2:11-14).  And so that part of God's kingdom has a pitifully small spiritual productivity.

They are like children grabbing precious gifts and treating them like trivial toys, soon losing interest.  Anybody who fails to be deeply impressed by the sacrifice of Jesus, as the substitutionary punishment for our sins, has no basis for growing in humble servant-hearted relationship with God.  If they cannot see the sacrifice of Christ they will not want to sacrifice anything which makes them feel good or great.  That is the reason why the apostles keep writing, “I want to remind you …” (1 Corinthians 15:1;  2 Peter 1:12) because we so easily forget what God says, and the sacrifice Jesus has made for us, when we are preoccupied in our own little worlds.

Alas such Christians are everywhere: they can hardly be called followers of Jesus, because they make no real effort to do so.  Yes, they go to church where they find a convenient social group.  But put them in the workplace, and they are indistinguishable from well-mannered unbelievers.  They cannot see any reason to be different, because they have forgotten the sight of the bloodied Jesus dying in agony on that cross for them.  What terrible spiritual unproductiveness.  It is high time to see the Christian life through Peter's apostolic lens which is focussed on the cross, and decide to repent and change.