Haste Makes Waste: to act too quickly causes a mistake and end up with poor result
Example: We should keep in mind, always careful with our work. After all, haste makes waste.
Hat Trick: When one player scores three goals in the same hockey game. This idiom can also mean three scores in any other sport, such as 3 homeruns, 3 touchdowns, 3 football goals, etc.
Example: After two election victories the government clearly has hopes of a hat trick.
He Lost His Head: to lose control, or angry and overcome by emotions
Example: My boss usually stays quite calm in meetings but he just lost his head in this time.
Hear It On The Grapevine: to hear something informally and unofficially by means of gossip or rumor
Example: I heard it on the grapevine that the company has a plan to move to a new country.
Hear something straight from the Horse's Mouth: to hear something from the authoritative source.
Example: I have heard some information yesterday, and it's straight from the horse's mouth.
Here today, Gone tomorrow: It's important or present now, but nobody know in future
Example: A lot of new internet companies are here today and gone tomorrow.
High On The Hog: living in luxury with a lot of money.
Example: They are living very high on the hog after they got the jackpot.
Hit The Nail On The Head: to do or say exactly the right thing in the most effective and efficient way.
Example: He hit the nail on the head when he said the problem was the mis-communication.
Hit the sack / sheets / hay: go to bed or go to sleep.
Example: Hey Bob, you look terrible! What time did you hit the hay last night?