To be a loose cannon
To be unpredictable.
To be tickled pink
To be very happy.
To be as sick as a dog
To be very sick.
To be in the same boat
To be in the same position or unpleasant situation as other people.
To hold someone's horses
To be patient and wait.
To be or feel under the weather
To not feel well.
Rise and shine
Wake up and be happy!
To keep someone's chin up
To be happy.
To pull someone's leg
To be just joking.
To get a slap on the wrist
Give someone a mild punishment.
Till the cows come home
For a very long time.
To be/feel down in the dumps
To be or feel sad or depressed.
Close, but no cigar
You were close, but you didn't make it.
To be Greek to somebody
To be impossible to understand.
To cost an arm and a leg
To be very expensive.
Hands down
Without competition.