The great moral that we learn from eating the bread of affliction [matzah] on Passover and from sitting in the Sukkah on Sukkoth - leaving a fixed dwelling for a temporary one informs us that we are not permanent residents in this world, but only visitors: here today and gone tomorrow. The principal hope for the faithful is the afterlife. Eating matzah, the bread of affliction, can be similarly understood, in that eating should be moderate and limited to bodily sustenance needs.
Dwelling in the sukkah and eating the bread of affliction are equal for both rich and poor in that the rich person cannot boast with his wealth. As the Bible says: "The rich and the poor meet together, the Lord is the maker of them all". Through these actions, therefore, the rich person will be familiarized with the poor person's situation, gain compassion for him and provide him with support. 'The sated person does not feel the pauper's hunger' may be a popular saying, but when a rich person eats the bread of affliction himself, not being accustomed to it all year, and also when he dwells in the sukkah, since the way of the rich is to dwell in beautiful and comfort abodes and he is now sitting in a roofless hut covered with only branches, his compassion is at once aroused, and he becomes convinced and sensitive to the pauper's distress.