I was so upset when I wrote the wrong date on my test, but my teacher said i didn't need to "make a mountain out of a molehill".
making a big deal out of something small
After her new haircut, she "looked like a million bucks"
looks really great
He decided to start studying and "turn over a new leaf"
begin again and change his ways
After I hurt her feelings, Lucy was "giving me the cold shoulder".
ignoring
Joe was behind on studying for his math test so he really had to "Hit the books".
study hard
joe got 100% on his math test. He said it was a "piece of cake"
Super easy
She can talk "until the cows come home" but it won't change my mind.
for a very long time