〜ずにはいられない

About

～ずにはいられない is a combination of a ず form verb, the に + は particles, and, いられない, the negative potential form of the verb いる.

～ずにはいられない is used to express that one "can't help but do/feel X".

E.g. ラーメンを見みると、買かわずにはいられない。 "When I see ramen, I can't help but buy it.”

～ずにはいられない is used for spontaneous actions or feelings, and shouldn't be used for volitional or planned actions.

～ずにはいられない expresses the speaker's feelings, so if it's used to describe how someone else feels, "seems like" markers such as ようだ, でしょう, or らしい are used.

E.g. ゆみとのデートが決きまったので、喜よろこばずにはいられないみたいだ。 "Because their date with Yumi was decided, it seems like they couldn't help but be happy."

～ないでいられない is also possible and is primarily used in spoken Japanese. ～ずにはいられない can be used in both spoken and written contexts.

Summary

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  ～ずにはいられない is used to express that one "can't help but do/feel X"

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  ～ずにはいられない should only be used for spontaneous actions or feelings

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  If ～ずにはいられない is used for someone other than the speaker's feelings, "seems like" markers such as ようだ, でしょう, or らしい are used

• 

  ～ないでいられない is also possible and is primarily used in spoken Japanese