en_tn_condensed/ecc/02/15.md

I said in my heart

Here the author refers to himself by his "heart" to emphasize his feelings. AT: "I said to myself" (See: rc://en/ta/man/translate/figs-synecdoche)

So what difference does it make if I am very wise?

The author uses this rhetorical question to emphasize that there is no benefit to being wise. This question can be written as a statement. AT: "So it makes no difference if I am very wise." (See: rc://en/ta/man/translate/figs-rquestion)

I concluded in my heart

Here the author refers to himself by his "heart" to emphasize his feelings. AT: "I concluded" (See: rc://en/ta/man/translate/figs-synecdoche)

is only vapor

"is only mist." The author speaks of useless and meaningless things as if they were "vapor." See how you translated this in Ecclesiastes 1:14. AT: "is as useless as vapor" or "is meaningless" (See: rc://en/ta/man/translate/figs-metaphor)