Lust is an pleasant emotion which makes you want to fuck.

It's natural.

Lust has a lot in common with anger - just being around certain people can bring it on intensely. Even just thinking about certain things can cause it. Also, like anger, it can cause a lot of problems if it runs out of control. Although it's not acceptable to mention it, feeling a righteous anger can be very pleasing, and in the same way feeling lust, although dangerous and intense, can be very nice. It's the intensity and possible rampaging nature of lust that caused successful societies to try to restrict it. The old way of restricting it was just a blanket ban on it, but gradually society is learning ways to allow lust in a non-harmful way.