Is it the pedal or the crank arm? I'm presuming the crank arm, since you wouldn't tighten a pedal with a socket wrench.
If the crank arm is coming lose regularly then most likely the "socket" in the arm, where it attaches to the crank axle, has become deformed from riding it loose.
But it's possible that you've just not been tightening the crank bolt tight enough -- it needs to be VERY TIGHT. (The Park Tools website has torque specifications for many brands, if you want to look there.)
You can lessen the chance of the bolt loosening by using a removable thread lock compound on the bolt. Also, if the crank axle has square (vs splined) ends and the crank arm socket has become badly deformed, a clever person can make shims from a pop/beer can to eliminate the "play" -- not a permanent fix, but enough to squeeze a few more months of use from the setup before you must replace the crank arm (and possible the crank axle).