Those sections of the catechism raise their own problems.
If we are talking suffering for eternity, I have a real problem with the idea that a person is capable of fully appreciating the gravity of their action absence a true effort, fully informed and done knowingly, with a purpose of defying God.
First, such an action, considering the gravity of eternal punishment, is irrational by definition in any example I can imagine( this the possibility of Hell is for those circumstances I cannot imagine).
An irrational mind is diminished by definition. Imputing culpability to an irrational thought process and behavior still posseses the same impediment to appreciation of " imputing" culpability, because the tool, the mind, is diminished I appreciating it also. That the mind was not capable of recognising fully, the gravity of the action in the first instance implicated the very same deficit regarding the sections you cite. Logically it is the the incapacity to fully appreciate the two catechism sections you cite at the moment of the Actus Reus.( Sin) that represents the diminished capacity in the first instance.
Which gets you to God’s purpose. Julian of Norwich speaks of sin as behovely. It is worse than hell, and at the same time it speaks to sin in God’s purpose as a vehicle to discern and appreciate right living.
God is good. We achieve salvation not because we are good but rather because God is good.
I tend to believe mortal sin is rare in the eternal damnation sense. Right or wrong, I feel confident that life is not a gauntlet of gotchas because my belief in God’s goodness won’t allow it.
So how does this translate?
Those sections you cite are certainly serious consideration. Don’t feign. Keep yourself in conscientious practice. We have an obligation to improve ourselves.
That said, my belief is God wants us to transform. Transformation is ultimately the persuit of internalizing Christianity. I heard the idea that we don’t think ourselves into right living, we live ourselves into right thinking, long ago. This simply means it is the practice of our faith that allows us to follow those words in the catechism. Loving one another, as Jesus loved us has to be more than words, and obligation, and sacrifice. It needs to be internalized. We need to engage each other with charity and mercy. Not as an obligation, but as a desire that flows more and more naturally from who we are. Transform! Then I think you find you have already gone a long way complying with catechism when you go back and read it.