Any one: Paul is not thinking of any particular individual here, but rather “any Christian,” male or female. Good News Bible uses “you” forms to avoid exclusively male reference.

Die Bibel im heutigen Deutsch restructures this verse to give another imperative like “we must” in other verses. It says “so be careful: anyone who thinks that he is standing firm should take care that he does not fall.”

Good News Bible correctly adds “firm” to bring out the meaning of stands.

As in verse 7, fall does not mean simply to stumble, but rather to fall in such a way as to be destroyed.

An alternative translation model for this verse is:
• Any Christian who thinks that he is secure in his faith had better be careful that he doesn’t fall (or, fail).

Quoted with permission from Ellingworth, Paul and Hatton, Howard A. A Handbook on Paul’s First Letter to the Corinthians, 2nd edition. (UBS Handbook Series). New York: UBS, 1985/1994. For this and other handbooks for translators see here .