How does laser cooling work?

Oops ... no so. I think. When an atom/molecule absorbs a photon it imparts on average half of its momentum because of the reason you gave ... relative direction of atom/molecule to laser. Still a gain on average. So what causes the cooling? It is when the photon leaves the atom/molecule shortly after. All of the momentum of that photon comes from the atom/molecule. So the net momentum from one absorption-emit cycle is an average of minus half the momentum of the photon. From what i understand is a momentum changs that is about 3000 times stronger than gravity. But please check this. I'm not a physisist.  Please let me know.