This is the time for evaluation and rededication. We begin by regretting past mistakes. Regret isn't guilt. When money falls from my pocket, I regret the loss, sew up the pocket and go on with life. I mustn't waste time with guilt.
Mistakes are too costly to repeat.
Our mistakes alienate us from ourselves and estrange us from others. The regret of past mistakes give substance to new intentions. For the Jew, it is with great joy that we come home to ourselves, to the people we love, to our Father in Heaven. Rosh HaShanah is a time of joy. On the day of Moshe's death he assembles the whole Jewish people and creates a Covenant confirming the Jewish people as the Almighty's Chosen People for all future generations.