In Zechariah (3:7), Hashem promises Yehoshua the Kohen Gadol that if he walks in Hashem's ways and keeps His charge, he will be granted the ability to rule Hashem's house and guard His courts. ונתתי לך מהלכים בין העמדים האלה - And I will grant you "walkers" among those "standing ones." According to Rashi, this means that Yehoshua's children will be righteous and permitted to move about amongst the angels.
The terms used in this passage highlight the distinction between humans, described as "מהלכים" - walkers, and angels, referred to as "עמדים" - standing ones. It underscores the fundamental difference between humans and angels; angels will forever remain on the level of holiness in which they were created, whereas humans are constantly in motion.
The essence of humanity lies in continuous movement, rising and falling both spiritually and physically, and experiencing fluctuations and changes. This characteristic sets humans apart from angels, who are static and unchanging in their holiness.
The Rebbe Reb Bunim of Peshischa taught his disciples that since the essence of man is that he is either progressing or declining, failure to improve spiritually is in itself a regression. We must remember that there's no standing still in one's life-journey, and that a day in which we haven't advanced, we've deteriorated.
Shlomo Hamelech said (Proverbs 15:24): ארח חיים למעלה למשכיל למען סור משאול מטה - For an intelligent man, the path of life leads upward, in order to avoid the nether-world below. The Vilna Gaon explains this according to the above idea, saying that the path of life leads either up or down - it's never neutral. A wise man always works his way up, because he knows that if he does not aim to ascend, he will inevitably end up in "the nether-world below".
