Decorous
(adj.) Proper; in good taste
-Two Unique Sentences-
Whilst eating with the king, the guest was quite decorous.
Although she was agitated by the gossip, she kept a decorous demeanor
-Two Synonyms-
Well-manneredHonest
-Two Antonyms-
Indecorous
Unbecoming
"You're in my house" Obama shuts down a heckler during speech