Having reached the worlds of those who did good deeds, and having lived there for many long years, one who has fallen away from yoga is born again in the home of people who are pure and prosperous.
Explanation
Krishna is answering Arjuna's worry about what happens to someone who sincerely begins yoga (spiritual discipline) but doesn't complete it. Such a person first enjoys the worlds of the virtuous (puṇya-kṛt), then is reborn into a good, comfortable family. Commentators generally take "eternal years" (śāśvatīḥ samāḥ) to mean a very long time, not literally forever.