There is a verse in Psalms 89:3 that says, עולם חסד יבנה, that the world is built on Chessed, acts of kindness. Hashem’s sole purpose in creating the world was to benefit mankind. G-d gave men a chance to serve Him only so that He could then reward them with Divine kindness. This concept was seen very clearly in the case of Noach and the flood. The Torah tells us that the world was filled with חמס, corruption before the flood. It was full of theft and taking from one another with no limits. This needed to be rectified by the year spent in the ark.
Rav Eliyahu Dessler pointed out that Noach and his family that were only eight individuals, were involved in Chessed, day and night for the entire year. He claimed that they fed thousands of animals around the clock, according to each animal’s needs. Everything needed to be timed just right so that the animals did not get violent. This was meant to offset the cruelty and selfishness of the generation. We find an example from Abraham where he was distraught on that hot day, when there was no one around to give some kindness. The righteous live to give and help others. The wicked only take, and never give of themselves. For the world to exist as it should, it must be based on loving kindness and helping others. The rewards for Chessed are immeasurable, but most of all, it gives the giver a strong feeling of contentment and satisfaction. It is clear what King David meant in Psalms, when he said that the world was built on Chessed.