lend someone a hand: help someone.
"I can't do this alone. Can you lend me a hand?"
a let-down: a disappointment; something that's very disappointing.
"It must've been quite a let-down not to be chosen for that job.
I know you really hoped you would get it."
Let sleeping dogs lie.: Don't cause problems by doing something when it isn't necessary.
"I know that what Julie said made you angry, but let sleeping dogs lie.
If you say or do anything, you'll only make things worse."
live from hand to mouth: survive on very little money; have only enough money
to pay for basic needs.
"Chuck and Alice are living from hand to mouth since Chuck lost his job."
live and let live: don't unnecessarily make things difficult;
do as you wish and let others do as they wish.
"I'm not going to criticize Alice's family just because their habits
are a little strange. My motto is 'Live and let live.'"
a low blow: a big disappointment.
A: "Fred seems depressed. Is he OK?"
B: "He's OK, but not good. It was a low blow for him to be laid off from his job."
lousy: terrible; very bad.
"Why did you speak so rudely to your grandmother? That was a lousy thing to do!"