Is 스스로 a pronoun or an adverb?

 ANSWER: It's an adverb.

스스로 is an adverb that means "by oneself," "by himself," "by herself," "by yourself," "by themselves," "by itself," "in person," or "on its own," and it is used before the verb and after a noun or pronoun, but many Koreans mistakenly use it as the pronoun.

Today, in Naver's Chinese Character Dictionary, I looked up the phrase 불기자심 (不欺自心), which can translate as "Don't kid yourself" or "Don't deceive yourself," and found the following Korean definition:

스스로의 마음을 속이지 말라는 뜻으로,스스로에게 엄(嚴)하고 정직(正直)하게 자신(自身)과의 약속(約束)을 지키라는 말

Notice that Naver placed the possessive marker 의 after 스스로, forming 스스로의. That means Naver is treating 스스로 as a pronoun meaning "oneself" or "yourself. That is wrong. Instead, the sentence should be written as either [당신] 스스로 마음을 속이지 말라 or 자기 마음을 속이지 말라, which can translate into English as "Don't kid yourself" or "Don't deceive yourself." Also, instead of 스스로에게, it should be 자신에게.

Moreover, the sentence was written backwards, for some reason. In other words, the last part of the sentence should come first.

So, this is how I would rewrite the above Naver definition of 불기자심 (不欺自心) HERE:

자신에게 엄(嚴)하고 정직(正直)하게 약속(約束)을 지키라는 뜻으로 자기 마음을 속이지 말라는 말

"It means 'Don't fool yourself,' meaning one should promise to be strict and honest with oneself."

Koreans seem to be trying to write English-style expressions in Korean, which is resulting in awkward Korean sentences that are harder to understand.

Seeing sentences like the Naver definition above makes me wonder about the future of the Korean language.

From Dong-A's Korean-English Dictionary