Rosh Hashana

Question

Rabbi, I realize that this is not a site for philosophical issues, but I would really appreciate hearing your explanation of the following question: Judaism teaches that G-d decrees the fate of every individual on Rosh Hashana (and seals it on Yom Kippur). It is determined how much money someone will make during the year, his life and health, etc. This leads me to two questions: 1. A whole tractate of the Talmud is called Taanit, which mostly speaks about how people would fast for G-d to provide rain. If G-d had already decreed how much rain would fall, which means how much food and sustenance the people would have during the year, what is the point of fasting? And if fasting is effecting (as it apparently is), then what was the point of a Divine decree having been made in Rosh Hashana? Rather, Judaism should teach that G-d judges every person every day and not on Rosh Hashana. This leads me to a general question: if everything is pre-determined on Rosh Hashana, then it seems that it doesn't make a difference whether a person works hard or not, takes care or neglects his health, etc. After all, everything has already been decided. This question is not about free will and Divine Providence, but rather about Divine decrees taking place in Rosh Hashana. Can they be changed? If yes, only through spiritual or also through natural means? And if they can, then what is the point of having Divine decrees established during this time of the year if they can be changed throughout the year. I would really appreciate your insight about this matter. Thank you Rabbi.