second set of tablets represents never giving up hope..

Moses and the Israelites receive the Torah (a complete understanding of reality) on Mount Sinai. soon after, the Israelites made a mistake and spiritually fell to the lowest of Levels. After spiritually falling (giving up all hope) the Israelites were given another chance but this time (Exodus 34:1) Gd said to Moses; "Carve yourself two tablets of stone". Teaching all of humanity that Gd blesses us with knowledge, wisdom, vision etc... but it's our responsibility to "carve out through action" the reality we want to experience in life.