Passage
we not looking to the things seen, but to the things not seen; for the things seen <FI>are<Fi> temporary, but the things not seen <FI>are<Fi> age-during.
2 Corinthians 4:18 (YLT)
Nearby Context
2 Corinthians 4:16 wherefore, we faint not, but if also our outward man doth decay, yet the inward is renewed day by day;
2 Corinthians 4:17 for the momentary light matter of our tribulation, more and more exceedingly an age-during weight of glory doth work out for us--
2 Corinthians 4:18 we not looking to the things seen, but to the things not seen; for the things seen <FI>are<Fi> temporary, but the things not seen <FI>are<Fi> age-during.
Study Lenses
The verse centers on "looking", "things", "seen", and "temporary". It is saying that the verse draws attention to "looking" and "things", so its meaning should be read from those terms before moving to application.
The prior verse says "for the momentary light matter of our...", giving immediate footing for "looking" and "things". In 2 Corinthians context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "looking" and "things" with trust shaped by these words, not by a vague optimism outside the passage.