अन्वयः

मर्त्य: a mortal, मृत्युकाले at the time of death, यथा as, विपरीतानि very differently, सेवते he will resort to, आत्मनः your own, पथ्यम् whatever is beneficial to you, श्रेयो वा your welfare, न समवेक्षसे you are not able to foresee.

M N Dutt

As one dwelling on earth perceives objects in their reversed relations at the time of one's death SO you do not perceive what is for your good or profit. Those moribund do not relish what would do them good.

Summary

At the time of death, mortals behave very differently. They act contrary to their own welfare. Likewise you are not able to foresee what is beneficial and good for you.

पदच्छेदः

न	न (अव्ययः)
नूनं	नूनम् (अव्ययः)
चात्मनः	च (अव्ययः)–आत्मन् (६.१)
श्रेयः	श्रेयस् (२.१)
पथ्यं	पथ्य (२.१)
वा	वा (अव्ययः)
समवेक्षसे	समवेक्षसे (√समव-ईक्ष् लट् म.पु. )
मृत्युकाले	मृत्यु–काल (७.१)
यथा	यथा (अव्ययः)
मर्त्यो	मर्त्य (१.१)
विपरीतानि	विपरीत (२.३)
सेवते	सेवते (√सेव् लट् प्र.पु. एक.)

छन्दः

अनुष्टुप् [८]

छन्दोविश्लेषणम्

१	२	३	४	५	६	७	८
न	नू	नं	चा	त्म	नः	श्रे	यः
प	थ्यं	वा	स	म	वे	क्ष	से
मृ	त्यु	का	ले	य	था	म	र्त्यो
वि	प	री	ता	नि	से	व	ते