Then you understand neither forgiveness or mercy.
While there are plenty of examples of consequence of sin in Scripture, it's usually earthly consequence, not a loss of salvation like Catholicism teaches.
Catholicism makes so much of salvation conditional on works that nobody can ever be sure if they're coming or going.
It makes a mockery of the finished work of Christ on the cross.
Please do not attempt to determine what I do or do not understand. That is mind reading. It does raise the question if you understand repentance and contrition?
Of course Christ's sacrifice was alone sufficient for all to be saved. However, if sufficiency was all that was necessary then all would indeed be saved from the moment of His death and resurrection.
I reject your characterizing and equating all that we must contribute for our Salvation as the works. The works referred to in Scripture are those acts necessary for compliance to the Old Law. The Catholic theology was best expressed by Fr, John Hardon:
Cooperation with grace, therefore, is our answer to the prior love of God. This responsiveness becomes more self-sacrificing in proportion as we understand more clearly how generous is the invitation; and how undeserved, because gratuitous, is the gift we possess (in sanctifying grace) or are offered (in actual graces). How ungrateful we are if we resist the advances of infinite mercy or lose the divine life we received.