If you're reading texts of this complexity, azhu, I'm surprised that you're confused about finding two verbs with different subjects in the same sentence. You must have encountered this many times in the course of your reading.
The subject of 'attain' is 'they' ('a person's inner concerns') and the subject of 'will be' is 'one's external concerns'.
'My brother likes butter but my sister prefers margarine.'
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