Mine are hard to turn some times too. I just grab it with both hands and turn. Dont push or pull it out of line with the socket. If you still think it might break then spray a little CRC, WD40, ect. Make sure its not fixin to come on w/ timer ect. and dont let any spray drip or get in the tank. Cover it up somehow.
Why not check out your electrical store, I'm pretty sure they make some type of electrical socket lube. I have a tube not sure what it's called, but it also prevents any corrosion buildup