The dictionary definition of temperance is: "moderation or self-restraint in action, statement, etc; self control."
So temperance is moderation and self-restraint in action, self-control. It can mean moderation , self-control in appetite, relationships, abstinence from alcohol, or any other addictive habits.
God wants us to be temperant. Galations 5:23 says " meekness, temperance: against such there is no law." He wants us to be temperant, to have self-control . In appetite, temperance means not being a glutton, and not eating the things that are bad for you. In addictive habits, it means abstinence abstaining from the things that harm your body.
Temperance is one of the 8 laws of health , because it important to good health. Your body can't be healthy if you don't practice temperance. Alcohol , gluttony, smoking,etc. are not good for our bodies. So if we are temperant, our bodies will be healthy!