One of the preparations before going for the Sacrament of Reconciliation is to use the 10 Commandments for the examination of conscience.
Breaking any of the 10 Commandments is indeed a grave sin.
Hence not going for Mass on Sundays, disrespect for parents, stealing, adultery, all these are grave sins. Blatantly grave.
But what is blatant can be equally destructive as what is subtle.
We avoid obvious grave sins, yet we can forget that there are sins that are not so obvious that will cause us to trip and fall.
In today's gospel parable, the Pharisee was proud that he did not commit any grave sin; in fact he did credible deeds.
But why was he not at rights with God?
As always, pride comes before the fall.
His problem was spiritual pride - he called another person a sinner without acknowledging to be one himself.
He propped himself up, at the expense of another person.
It was subtle, but evil. So we need to watch ourselves.
If we think we are virtuous, are we also getting self-righteous?
We can make sacrifices and perform credible deeds.
But what the Lord wants is not sacrifice. What He wants is our love for Him and for those around us.
And if we should fall, then we only need to turn to God and say: God, be merciful to me, a sinner.