The Dirty Papist

A man had two sons.
He came to the first and said,
'Son, go out and work in the vineyard today.'
He said in reply, 'I will not, '
but afterwards changed his mind and went.
The man came to the other son and gave the same order.
He said in reply, 'Yes, sir, 'but did not go.
Which of the two did his father's will?"
They answered, "The first."
Jesus said to them, "Amen."

This gospel passage, where the vintner hires workers in the morning and at midday and in the evening and pays them all the same, tells us amongst other things that whether we come early or late to the party, there is no partial reward upon admission to heaven.
I think this makes a reasonable contribution to the argument that we don't gain heaven through our own efforts; if God is not fair, then at least He is generous, and whenever you accept His invitation to the vineyard, at the end of the day you'll receive the day's wages.
Then, though, we are presented with the question Jesus posed to the chief priests and elders in another passage (which are actually mass readings a week apart for year A, I think).  Here's another vintner, one with two sons he tells to go work in his vineyard.  One says he won't do the work, but relents; the other makes an obeisant sign and then reneges.  Which one did his father's will?  In terms of the analogy, which one would enter the kingdom of heaven? The one who did his father's will.  Not the one who said he would.
I would hope that this episode would serve as a counterpoint to certain schools of thought that look at the parable as a proof text (one of several, I should say) for easy and irrevocable salvation bought by the recitation of a verbal formula.  When asked to explain someone who invites Jesus into his heart and at some subsequent point in his life seems to succumb to temptation and embraces malice and hedonism until the end of his life, the only possible answer given is "He must never have gotten saved in the first place."
It's very easy for the next thought to be "but that would never happen to me; I meant it in my heart when I asked Jesus to become my personal Lord and Savior."  
Savvy:  Christians are offered every same temptation as pagans and other unbelievers.  Committing sin remains a very real possibility for the duration of every person's mortal life.  An adulterer may reasonably expect his life to be destroyed by vices other than alcoholism or rage, but if he says "I'm turning over a new leaf, so help me God!" and then completely doesn't, then maybe he never meant it...or maybe it's just not that simple.
After all, not all who cry "Lord, Lord!" will be saved.  God will do everything to bring you to paradise except force you to go.  If you make a habit of making promises you don't keep (which is what the disobedient son did), your promises will come to naught; they won't fool God, and they won't fool you.  If you make a habit of breaking promises to do the will of God, you won't find yourself inclined to do or submit to His will for long.
In the first parable, even the people hired at the end of the day worked that last hour.  The vintner did not pay them in advance.
Okay, okay; some will say "He's saved despite the evils he commits" and others even "Christ's blood has it covered so those aren't really sins."  To the former I say one who endeavors to reject the graces of living a good life will not be disposed to accept the grace of salvation, no matter when either is offered; and to the latter I say a pardoned debt extinguishes deficit expenditures without defining them away.  To the former I say thus does presumption endanger the soul of the lazy believer, and to the latter I say you have no dog in this fight from the very beginning of it.
But again, while we are not expected or required or able to achieve the sanctity of heaven by our own efforts, we are expected to make hay during whatever sunshine still remains in the day.  Blessed Teresa of Calcutta said we are called to be faithful, not to be successful.  We are not called to earn justification and righteousness, we are only called to do the work.
Just as Paul said "Husbands, love your wives as Christ loved the Church and gave Himself up for her," it is to husbands given the responsibility of dying for their wives; it does not then follow that no man who fails to consummate martyrdom for his wife has failed as a husband.  He is called to that duty, not required to execute it in the extreme in every case.