If you're equanimous, you're serene and calm. Some people meditate or do yoga in an attempt to be more equanimous.
People who are equanimous seem enviably composed and balanced. You might be equanimous about some things, remaining calm when your dog barks or your smoke alarm goes off, but less equanimous about others. Many philosophies and religions, including Buddhism and Hinduism, emphasize the importance of striving to be equanimous. The word is related to equanimity, both from the Latin aequanimis, "mild or kind," or "even minded."