The Torah associates Succos with happiness more than any other holiday. It is the holiday we are told to rejoice on. It is the season of our rejoicing.
What makes Succos so happy? Why is it happier than Pesach or Shavuot, the other two of the three Regalim?
Pesach and Shavuot were both marred by rebellion and strife. At the sea, some Jews shouted at Moshe, "Were there no graves in Egypt, that you brought us to die in the wilderness". After the giving of the Torah, some made a golden calf. But Succos was free of any such strife.
When G-d settled the Jews in huts, there were no arguments.
This too is why the Clouds of Glory, which some believe Succos commemorates, received their own holiday, but not the miracles of manna or water. Both of these miracles were met with protests and complaints. But there were no protests or complaints over the Clouds of Glory.
Where there is argument and strife, there cannot be happiness.
Succos is the time of our rejoicing, because the Jewish response to these miracles was at its purest. It is fitting that the clouds were in honor of Aaron the High Priest, who loved peace and pursued peace, whose service was to love and bless the people. Succos comes from the same love and blessing.
The second day of creation is not described as good by G-d because the water was divided on that day between sky and sea symbolizing strife. And strife cannot be called good. What is good is the completion.
Pesach, which symbolized water, provided man's most basic necessity. Moshe was saved from water and he led the Jews through water and helped provide them with water. Water is a basic necessity of survival, but having a basic necessity does not refine human character.
Shavuos, the next holiday in the cycle of three, celebrated bread and provided Torah. Satiation sustains a person. It gives him "something to chew on". But it doesn't provide a final resolution.
Succos provides the "house" which completes a person's place in the world. Bread and water isn't enough. It's a home that creates harmony. Succos completes the process with the final redemption, the battle of Gog and Magog to take place in Tishrei and the final rejection of the Sukkah by the world. And the ultimate Sukkah is Sukkat David, the Temple. When that is raised up again, then strife comes to an end and the purpose of the person is clarified.
It is the home that gives objects and people meaning. And so the water and the manna were accompanied by strife, but not the Sukkah. With Succos, there is home and happiness because the joy is complete.