Musar su Salmi 91:7

After the דינין and משפטים in this portion have been concluded, the Torah turns its attention to Israel's journey towards the Holy Land with (23,20,) הנה אנ כי שולח מלאך לפניך. "Here I am sending an angel ahead of you." Shemot Rabbah 32,6, quotes Psalms 34,8, חונה מלאך ה' סביב ליראיו ויחלצם, "the angel of the Lord camps around those who fear Him, and rescues them." When man performs a commandment of the Torah, G–d creates an angel to protect that person. When said person performs two commandments, G–d provides two angels to protect him, since we are told in Psalms 91,11, כי מלאכיו יצוה לך לשמרך בכל דרכיך "for He will order His angels (pl) to guard you wherever you go." If a person performs many commandments, G–d gives him half His camp as is written: "A thousand may fall on your left side, ten thousand on your right side, but it (disaster) shall not reach you" (Psalms 91,7). This half of G–ds camp is described in Psalms 68,18, i.e. that "G–d's chariots are myriads upon myriads, thousands upon thousands."

In other words, such people penetrate to one half of the ribotayim mentioned in Psalms 68,18. This is why the verse in Psalms 91,7 is quoted, since it speaks of revavah =ten thousand, instead of rivotayim, twenty thousand. The meaning of Kohelet 6,6, in which even twice a lifetime of one thousand years is described as ultimately futile, is that unless one achieves רבבה, the level of עולם הבריאה, one has failed to achieve one's goal, i.e. half the “full yud.”