What do you think, if we already have ticked the things of being a Christian, we are already saved? We can have a list of the things to be considered a believer and we can just tick each one. Prayer-tick, bible-reading-tick, confession-tick, mass and communion-tick, charity works-tick. Then after we have done that, are we now sorted for salvation? I think, we never know, we are not sure.
Because being a believer is not about ticking of the things we have to do but it is about conversion of the heart, this is true obedience.
This is what the gospel of the parable of the two sons is telling us. The elder son is the one who does the will of his father because he has conversion. That is why, Jesus is telling his listeners that the sinners, prostitutes, tax-collectors will be first to enter the kingdom because they changed their hearts.
Therefore, God is not very much after for what we can do for him but He is after for the conversion of our heart. But the fact remains that this is a lifetime process of conversion. That is why we need grace. This is the meaning of the Second Reading. Christ came and became one of us because through Him we will be converted. Human effort is not possible. It is only possible through Christ. Humility to accept that we need grace is an ingredient towards conversion.
I am not saying that we stop attending mass or praying and doing what is expected of being a Catholic but we have to recognise that our desire to be like Christ is the reason we are doing these things.
Being a Catholic is not just about ticking of the things we have to do, but it is about having a heart like Christ.