A press of festivals dominates Tishrei. We haven't even had time to recover from the last one before we must immediately prepare for the next. First Rosh HaShana, then Yom Kippur, then Sukkot, and finally Simchat Torah. The packed proximity of these festivals to the others indicates some conceptual relationship between them. Unquestionably, it is not just a coincidence that they are all together this way.
Rosh HaShana's relationship to Yom Kippur is prominent and well-known. On Rosh HaShana, we are judged. On Yom Kippur, we find ourselves begging for a second chance after that judgment. How does Sukkot fit in? Our rabbis answer this question in two ways, referring to the mitzvah of lulav and etrog. The first (and most prominent) is that the lulav constitutes a prayer for rain. It consists of various types of greenery that rely on different quantities of water, illustrating different levels of reliance on rain. However, fundamentally, they all need water, and so do we. Sukkot continues the themes of Rosh HaShana and Yom Kippur, except at a communal level instead of for an individual. Rain doesn't happen to each of us separately. Its effect is collective.
The second explanation is diametrically opposed. Our Rabbis say that we lift the lulav to celebrate being forgiven. We are so overcome with joy after Yom Kippur that we begin to dance with a series of fruits from our garden, signifying the bounty we expect in the coming year.
These two explanations of the mitzvot of lulav and Sukkot, though in tension, work together. I once heard from my teacher, Rabbi Aharon Lichtenstein, that Jewish celebration includes rejoicing and prayer for the future. We both thank Hashem for His goodness to us and ask that He continue His beneficence.
Just so, may the coming year continue to afford us both opportunities for joy and the ability to continue planning and praying for the year to come.