There is a mitzvah in the Torah to try to be like God. One of God's characteristics is that He "sustains all the living with kindness." Not only does He give us so many things for free, but He lifts our spirits when we are down.

A person should try to emulate God both by giving in the physical sense, and by giving of himself to lift the spirits of those who are down. The Rambam writes that there is no greater joy in life than the joy one receives by lifting and reviving the spirits of those who are burdened by life's travails. The Torah teaches us that on Sukkot we should rejoice with our sons, daughters, our male and female household help, the orphans, widows, strangers and Levites (the spiritual leaders of the nation).

Rashi explains that if we look after the Almighty's four (the orphans, widows, strangers, and Levites), He will look after our four (our sons, daughters, and male and female help), blessing us and them with joy and inner peace. If we take the opportunity to be God-like and sustain all those around us with kindness, God will reciprocate in kind.

In fact, Sukkot comes after Yom Kippur because in order to be God-like, we need to be "big." We can't go through Yom Kippur properly and come out with grudges. The blessings which we receive are in direct proportion to the amount of effort which we invested.