This is true. The seven deadly sins aren't sins in themselves. They're considered to be the seven root causes of sin in general. If you substitute the corresponding virtue ( humility, charity, kindness, patience, chastity, temperance, and diligence) into your personality for the personality trait that causes you to do evil things, you become a better person.
So, there becomes two things to conisder. Zooby's question requires a person not only to be willing to give up one those personality traits, but they also have to consider that they'll have to take on one of the virtues in its place (since nature abhors a vacuum).
Worry not. There's a different list of seven deadly sins that includes your favorite. Solomon's list of deadly sins:
A proud look.
A lying tongue.
Hands that shed innocent blood.
A heart that devises wicked plots.
Feet that are swift to run into mischief.
A deceitful witness that uttereth lies.
Him that soweth discord among brethren.
Among the original sins/virtues, I think I'll go the other way. I want to give up chastity and take on lust in its place. I'll never give up psychiatric depression - especially if I have to replace it with diligence!