Sforno on Deuteronomy 30:20/ספורנו על דברים ל׳:כ׳

1ולדבקה בו, meaning that all of your activities during life on earth should be focused on giving glory to His name.

2כי הוא חייך, for your cleaving to Him is your real life, the reason why you will enjoy eternal life;

3ואורך ימיך לשבת על האדמה, during the transient life on earth, during which through study, serious contemplation of your duties, and your performance of them you will qualify for the life awaiting you in the hereafter. Compare Avot 4,16 where we have been told that life on earth is merely to be viewed as a vestibule to the hereafter, a place in which one makes suitable preparations for eternal life in the Palace.