Question about 'Ramayana'...?

In the 'Ramayana', doesn't it seem strange that Ram wasn't aware of his divinity (Brahma had to let him know about his true self), but Sita knew who she really was? When Sita is asked to prove her chastity for the second time, she calls upon her own mother, the Earth (Sita was born from the Earth), to swallow her (as if she knew all along that she was never an ordinary human, but, in fact, an incarnation of Lakshmi). And after Sita leaves, Ram is grief-stricken, and it is Brahma who reminds Ram of his true self (that he was an incarnation of Vishnu, so he was never separated from Sita to begin with, nor will he ever be). Could someone please explain this to me? How is it that Ram didn't know he really was, but it seems that Sita knew who she really was? This is one aspect of 'Ramayana' that I just don't understand.