The Holy Progression

U'vichein tein pachdicha - FEAR! That is Rosh Hashana and Yom Kippur.

U'vichein tein Kavod - GLORY! That is Sukkos, in memory of the Clouds of Glory.

U'vichein tzaddikim yiru vi'yismachu - THE FEAR AND JOY OF THE RIGHTEOUS! That is Shmini Atzeres which Chazal say is the day where the Jewish People and Hashem have an intimate meal together to which no other nation is allowed entrance. This is reminiscent of the end of days where it says "Vinisgav Hashem livado ba'yom ha'hu".

[Rav Yechezkel Sarna Ztz"l in his "Dlayos Yechezkel"]