Everything you have means I have less. When a person feels like this, the very existence of other people bothers him. This is what is called sinas chinam - baseless hatred. Sinas chinam brings exile to the Jewish People. Two thousand years ago, the Second Beis Hamikdash was destroyed and we were exiled and dispersed all over the world because of sinas chinam .
Exile causes a person to feel rootless and destabilized.
Inevitably this negates his acquisitiveness. The punishment of exile cures the separation between people that is the manifestation of sinas chinam . By living in a temporary dwelling, we sensitize ourselves to the very temporary nature of our dwelling in this world. This process of living in the succah gives us the sense of vulnerability and instability which is the hallmark of exile. This feeling unifies the Jewish People and nullifies the selfishness that leads to sinas chinam, which was the reason for the verdict of exile in the first place.