Literature

Earl is a man in a cell with no windows . Would you explain these sentences to me especially the bold part ?

Earl said ,"Normally I would make some excuse about the light going quickly on winter
afternoons, but of course we are all candles here. And thank heavens, too. The
cells with windows may be filled with light, but they are unconscionably cold.
All you can do is watch yourself freeze to death. No, here we are merely
racing against Mr. O’Reilly’s return.”