तत्र तं बुद्धिसंयोगं लभते पौर्वदेहिकम्। यतते च ततो भूयः संसिद्धौ कुरुनन्दन ॥

tatra taṁ buddhi-sanyogaṁ labhate paurva-dehikam yatate cha tato bhūyaḥ sansiddhau kuru-nandana

There he recovereth the characteristics belonging to this former body, and with these he again laboureth for perfection, O joy of the Kurus.

In plain words: Krishna says that in the new life, the person gets back the spiritual progress they made before. With it, they work toward perfection once again.