Sentence:  ... 'Tis pitiful / To court a grin, when you should wooe a soul; / To break a jest, when pity would inspire / Pathetic exhortation; and t' address / The <WSD>skittish</WSD> fancy with facetious tales, / When sent with God's commission to the heart. 
Meaning of the word marked with <WSD> tags:  Wanton; changeable; fickle