fresh as a daisy
Well rested, energetic, as in I'm finally over my jet lag and feel fresh as a daisy. This simile may allude to the fact that a daisy's petals fold at night and open in the morning. [Late 1700s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.