Sentence:  A strange thing was that Bovary, while continually thinking of Emma, was forgetting her. He grew desperate as he felt this image fading from his memory in spite of all efforts to <WSD>retain</WSD> it. Yet every night he dreamt of her; it was always the same dream. He drew near her, but when he was about to clasp her she fell into decay in his arms. 
Meaning of the word marked with <WSD> tags:  To keep in possession or use.