Cruise control keeps you moving at a steady speed on the highway, and you should attempt to do the same at lower speeds as well. Nailing the gas pedal at every light, accelerating heavily and then standing on the brakes is more wasteful than the U.S. federal government.
Try to relax and drive smoothly with deliberate caution. Sure, it’s not as much fun as roasting the tires from a standstill but you will save money on fuel. In short don’t drive like a teenager.