Vices are based off the desire for some good, but they could not be vices if they attained this good in a complete manner. But to desire any good is to desire it as a whole, and so vices are characterized by implicit contradiction between what is sought and what will be attained. What are the unique contradictions of the various vices?
Pride: in seeking ones own excellence, we end up in the dark “humility” of embarrassment over our past failures, unhappiness over what we can achieve, self-loathing over our own inability to follow things through, and the perpetual dissatisfaction feeling of being cheated out of all the things we feel are due to us.
Envy: In seeking that we should be a source of good things for others, we come to hate that others have any good of themselves.
Gluttony: The desire to preserve existence destroys the very existence that we sought to preserve.
Lust: The desire for the pleasure of sexual union leads to dissatisfaction with and alienation from others.
Wrath: The desire for justice – which requires harmonious life with others – turns into a desire to crush others and lord it over them.
Greed: The desire for self sufficiency becomes an imprisonment to the things we think can grant it.
Sloth: By seeking the smooth activity of life, we lose the very activity that constitutes life.
Just Thomism 
E.R. Bourne said,
May 31, 2012 at 6:56 pm
James, this is an excellent post.
The contrast is striking. The desire for sexual union is essentially ordered towards others (the spouse and children), for instance, and yet it can turn instead toward pornography, a most isolating addiction.
From looking at each vice and how it destroys the very good that is sought, it appears that vice always consists in treating the self as the good for which all others exist. The natural desire is directed outward, but the turning of it inward breeds vice.