The requirement to "live" in sukot obligates us to "move into" it and performing as many of our day-to-day activities in it as possible. Thus, unlike other commandments, which involve only a particular limb of the body, the sukah involves the whole person. During Sukot, even mundane, weekday eating becomes a fulfillment of a commandment when performed in the sukah.
Furthermore, a home is a basic human need, secondary only to food and clothing. Besides fulfilling the need for shelter, a home is a tangible expression of our mastery over the physical world; as such, it is a vital component of the fulfillment of our Divine mission -- to make this world into G-d's home. Moreover, inasmuch as each of us is required to reveal Divinity in the world in a unique manner, as an expression of our unique Divine souls, a private home is an expression of the personal component of our Divine mission and an essential vehicle for our self-expression. Inasmuch as fulfilling this Divine imperative lies at the bedrock of our psychological makeup, the lack of a place to call home leaves us disoriented and unfocused. The sense of completeness we draw from our home is felt not only when we are in it, but even when we are outside it.
So when, during Sukot, the sukah becomes our home, our domiciliary self-completeness is invested with the holiness of the commandment of living in the sukah. This experience of living inside a Divine commandment and drawing our sense of self-completeness from it enables us to live the rest of the year "surrounded by G-d's commandments," i.e., sanctifying our entire lives, including their most mundane aspects.
Yet, paradoxically, while the sukah is given an element of permanence, it must be a temporary hut: its roof must be makeshift, and it cannot be taller than 20 cubits (9.6 m or 31.5 ft). This paradox conveys an important message: The experience of living in a temporary hut for seven days reminds us that life itself is ephemeral. The seven days of Sukot correspond to the basic human lifespan, described in the Psalms as consisting of 70 years. By recognizing life's inherent transience, we protect ourselves from losing our perspective in the illusion of permanence. We can then imbue the world with true permanence and meaning by transforming it into G-d's dwelling.
-- From: The Kehot Chumash