The Yehi Ratzon for today's parashah of the Nasi of Ephraim asks HaShem to vanquish our enemies in the merit of Ephraim. It also mentions and emphasizes peace between Ephraim (Moshiah ben Yosef) and Yehudah. (Moshiah ben David)
Tishrei also represents (to the best of my knowledge,) shkiah and nightfall, as well as Sukkoth representing Maariv, the evening prayer. It is a time of celebration and newness as well as a time of forgiveness when Teshuvah is most easy. Sukkoth is also the time of HaShem hiding us away from the world and celebrating privately with us. Simchat Torah also takes place in Tishrei.
So today is a day to rejoice with HaShem and His Torah. A day to ask forgiveness and appreciate newness.