Intemperance is when you can't do anything half way, or hold yourself back. You might describe your inability to eat a single slice of cake — instead, gobbling the whole thing — as intemperance.
When someone isn't able to temper — or moderate — his actions, he is at risk of intemperance. Your uncle shows intemperance when he yells furiously at everyone around him every time he feels angry, and your sister's intemperance might come out in her terrible shopping habit. The opposite of intemperance is moderation. The Latin root word, intemperantia, means "immoderation or excess," and was originally used in English to describe the weather.