Temperance: noun. moderation or self-restraint (without withdrawal) in action; habitual moderation in indulging natural appetites or passions.
“The most fundamental of the four cardinal virtues is that on which the other three (prudence, fortitude, justice) depend.”
Temperance is a foundational virtue that identifies us as followers of Jesus. Temperance, for the Christian, means loving Christ over self, and denying the self, escaping sin's grasp, to follow him. We must, as Christ's followers, pursue temperance as a foundational Christian virtue. The appetites of the flesh must be mastered. Paul actually says your passions must be crucified.
Temperance/moderation reminds us that good things come from God–so we can be thankful for them.
When we indulge the passions/appetites of the flesh, we make ourselves/our pleasure out to be the ultimate end. We are inheriting our own destructive kingdoms, not the Kingdom of God. A life of excess will always leave you wanting more, but satisfaction in life comes from being thankful for what you have.