הבל הבלים אמר קהלת " 1:2 – ייטב לב
הבל הבלים הכל הבל" – The root of the month of Chodesh Tishrei is things of the heart. Mitzvas Shofar of Rosh Hashana is "הבל הלב" "emanations of the heart." The main part of Vidui on Yom Hakippurim is the heart regretting the Aveiros. Vayikra 23:42 43" בסוכות תשבו... למען ידעו דורותיכם" Tur, Bach and Magen Avrohom (625) all say that "שיכוין בלב" one must have Kavanah with his heart that he is sitting in the Sukkah as a Zecher to Yetzias Mitzrayim. We Lain Koheles on Sukkos for Koheles tells us that we must work on our "הבל הלב", our emanations of the heart, and the month of Tishrei is filled with Mitzvos which we must use "הבל הלב" .