Humility lies at the core of the religious experience. It is imperative to realise our place in the cosmos (a small one), so we can approach G-d appropriately. Humility is also a central message of Sukkot. Sitting in a temporary house under a roof that cannot (definitionally) protect us from the elements drives home our dependence on the divine for everything in our lives. While the Sukkah is illustrative of our predicament, our inability to survive absent divine support is just as actual the rest of the year.
However, counterintuitively, Sukkot is also a reminder of what we can do well. It is not an easy festival. It requires extensive effort and much preparation in advance. It also requires some fortitude. If it gets a bit cold or just inconvenient, we must expend much energy on not just going inside. All of this is something that should genuinely cause us pride.
Sukkot is a dichotomy. We are both very, very small and very, very important. Our place is almost insignificant, yet our work has tremendous cosmic significance. We find this strange dynamic in many places in the chag. For example, we are told that the Lulav constitutes a prayer for rain as the species we wave are all reliant on rain. And yet, it is also a triumphant declaration that we were forgiven on Yom Kippur and can look forward to a good year. Similarly, in Hallel, desperate prayers for salvation bump up against joyous songs of thanksgiving.
Perhaps this is the true significance of the holiday. It is not just humility that is demanded of us, but pride in our achievements also. We can only progress into a year of spiritual growth when these two come together.