Sentence:  ... if I thought the sentiments of your last letter were not the sentiments of a <WSD>sickly</WSD> moment—if I could be made to believe, for an instant, that they proceeded from you, in a sober, reflecting condition of your mind—I should give you over as incurable, 
Meaning of the word marked with <WSD> tags:  Marked by the occurrence of illness or disease ("of a period of time").