If lusting after a woman is a sin, why did god make having sex so enticing?

I've always made a clear distinction between seeing a woman and merely appreciating her beauty, and mentally undressing her and/or fantasizing about having sexual relations with her. The latter I believe is what Jesus referred to as committing adultery in your heart. If I'm not married to her, I don't have the right to undress her either physically or mentally, and I don't have the right to sexually objectify her.