What do you do if your bearded dragon is too cold?

"No it's not ! In their NATURAL habitat - they'd only get about a 10 degree Celsius drop at night - YOU as the owner are charged with the responsibility of creating the same living conditions."

Not entirely true. Bearded Dragons originate from the desert, the day temperature (or your hot spot) should be between 90-120 degrees Fahrenheit. A 10 degree Celsius drop is 50 degrees Fahrenheit, that would be 40-70 degrees Fahrenheit from your "sun spot" temps. Desert temperatures are known to drop below freezing at night, especially in winter. Despite this I would never say let your dragon get that cold and most houses do not get that cold. Reptiles naturally go into a dormant state when temps cool down and when the sun comes up they move to a rock or high spot to bask and increase their internal body temperatures. So, if you are asking because you don't know if your heat light should stay on 24/7 then no, its okay to turn it off at night if your home temp is no lower than say 60F.