Literature frequently employs this sensory metaphor to illustrate the downfall of ambitious characters. From the "forbidden fruit" in religious texts to the tragic end of Great Expectations, the transition from sweet to bitter is a recurring motif. It signifies the loss of illusions. When a character spends their life chasing a dream only to find it hollow, the "bitterness in the mouth" represents the irreversible nature of time. You cannot "un-taste" the truth once it has been revealed.
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