Nǐ bié mà zìjǐ shì jiàngútou, tā gēnběn bù zhídé nǐ zhèyàng.
Stop calling yourself a fool — he isn't worth it.
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Insult — fine in fiction or strong colloquial speech, never in polite or formal contexts. Often self-deprecating in romantic contexts ('I keep going back to him, I'm such a 贱骨头'). Compare the milder 没出息 (méi chūxi).