Protective nature of the seven deadly sins?
 
The list of the Seven Deadly Sins in The Catholic Catechism of Christian Doctrine goes: pride, gluttony, greed, envy, sloth, lust and anger.  They are called deadly for each one is potentially a sin that all other sins are rooted in.  Avarice leads to stealing and the thief is proudly thinking she or he will get away with it.  That is two of the deadly sins.

If you feel threatened by the world and see it as posing threats to your happiness and emotional wellbeing, you will tell yourself that you are a fool so that it does not expect much of you. Telling yourself you are a fool is protective behaviour. There is enough to fear without fearing the alleged results of sin and everlasting punishment and fearing what God might do. Your fear will lead to hate against others. It is a timebomb. Acting a fool through the seven deadly sins is just as bad as labelling yourself a fool.
 
The doctrine of loving the sinner while hating what the sin says about the person is totally incoherent. To hate what sin says about the person is to hate the person. But because people want to hurt sinners and injure them they have to engage in protective behaviour (they are protecting themselves from themselves) by telling themselves that hating the sinner is not hating the sinner. They end up bullying those who see through their lies and those poor people end up condemned and punished while sinners go uncondemned and unpunished.
 
Pride protects you from the pitfalls of bad confidence in yourself and can be used to create an aura that scares bullies away. Pride is inevitable for our minds can only process some of the data that we receive so our vision is necessarily narrow and neglects the full picture. Yet we think we know more than what we do. We think we are more objective and honest than what we are.
 
Jealousy is about wishing you had something instead of another person having it. It is about a sense of superiority.
 
Lust protects you from dullness in your life.
 
Envy lets you know that you are missing something another has. Instead of enjoying what you have, you endure pain at what others have. It may be that you are simply unable to enjoy what you have and it's not down to envy. Thus you tell yourself that you are deprived because others have different or better things than what you have. This is protection from the fact that the problem is you - you cannot appreciate what you have got.
 
Laziness protects you from the struggles of life and of putting up with difficult people.
 
Gluttony comes from a sense that life is to be enjoyed so it is protecting you from unhappiness.
 
Anger is very protective. It is about feeling intolerant of what you consider evil. You want to be safe from attack and to live in a world that values your own values so you get angry if there is any violation of your safety and values.

You would why cowardice is not one of the vices.  Christianity says that courage is the virtue by which you decide to look after your neighbour though there is a real danger to your own wellbeing. It is a sin to love your safety more than your neighbours.  The vices are all about loving something you have more than your neighbour.  The trouble is that you are asked to love your neighbour so to love your wife or son or daughter as a neighbour seems warped.
 
The seven deadly sins are the sins from which the other sins including mortal and venial proceed. The other sins are made of them. But as the deadly sins have a protective role, it is foolish to argue that there could be such a thing as a mortal sinner. A mortal sinner needs to make his own heart fully black and godless but that cannot happen when sin is at least partly protective. His heart can only become grey.