The month of Tishrei is the "richest" month in the Jewish calendar. It includes the most awesome days - Rosh Hashanah and Yom Kippur as well as the happiest days - Sukkot and Simchat Torah.
Every Jew participates, in one way or another, in celebrating the High Holidays, which take place at the beginning of the Jewish year. These holidays give us a sense of renewal and serve to inspire us for the entire year to come.
Each holiday is not only a time of remembrance of a certain occasion in history, but also a recurrence of the original event. It is a time of reawakening of the special relationship between G-d and the Jewish people, and between G-d and the world. In order to commemorate the holiday properly and observe and experience it meaningfully, one must prepare for the occasion accordingly.
Rosh Hashanah is a time when we once again accept G-d's Kingship, and when the entire Creation, the Universe with all its creatures, is judged. Yom Kippur is the time when the Almighty forgives us for all our wrongdoing. Sukkot and Simchat Torah are times when we rejoice in the renewal of the relationship.
Therefore, we must be properly prepared for the judgment, worthy of forgiveness, and be able to truly cherish and value the renewal of a relationship bestowed upon us by G-d. In Jewish tradition, the entire month of Elul, preceding the High Holidays, is a month of preparation.
