Why is the holiday of Succot and the succah associated with happiness? Personally I view being exposed to the elements or other dangers to be unsettling, at the least.
The way of the nations is not the way of Israel. It is the way of most people to feel secure and unafraid when under the shelter of their own roofs. On emerging from their homes, their sense of security is diminished and they begin to feel fear.
Israel, however, is different. While in their own homes the whole year, they are concerned lest they become haughty and forget G‑d. When Succot comes, and they leave their homes to enter the shade of the succah, their hearts are filled with faith, trust and joy. Since now they are shielded not by their roofs but by the shadow of their faith and trust in G‑d.
This may be compared to a person who locks himself up at home for fear of robbers. Regardless of the strength of his locks, he remains afraid lest the robbers find a way in. Once he hears the proclamation of the King calling all to emerge from their homes to join the King and his retinue, he is no longer afraid. He opens his doors and joyously emerges to behold the King. For he knows that wherever the King is found, robbers are not. Thus, he is filled with tranquility and joy.
So too Israel, when they are in their homes throughout the year, surrounded by material comfort, they are afraid that indulgence may sneak in and rob them of their connection with G‑d. But during Succot, when G‑d Himself calls the Jews forth to celebrate the bounty given them by G‑d with the King Himself, together with the righteous Patriarchs present in the succah, they are serenely confident that their closeness with G‑d will not be diminished. On the contrary, it grows day by day through the seven days of Succot and crescendos in Simchat Torah!