The Catholic Church believes that it's normal and healthy to be attracted to and appreciate the opposite sex. That's not lust, and it's not considered a sin.
Lust is looking at, imagining, and even treating others as mere sex objects to serve your own physical pleasures, rather than as individuals made in the image and likeness of God. Lust is having someone become something merely to please you, in fantasy or reality.
The Church says that lust depersonalizes the other person and the one having the lustful thoughts. It makes both parties nothing more than instruments of enjoyment instead of enabling them to focus on the unique gift of personhood. And it seeks to separate, divide, and isolate what God intended to be united -- love and life, the unitive and procreative dimensions of marriage...
Chastity, the virtue that moderates sexual desire, is the best remedy for lust. Chastity falls under temperance and can help to keep physical pleasure in moderation.
Catholicism For Dummies by John TrigilioRecommended reading: Back to Virtue by Peter Kreeft. He examines the virtues in depth and also looks specific virtues and Beatitudes as antidotes to each of the seven deadly sins. Not a new concept but one that he writes about superbly (as always).
Next up ... Anger.