Body Idioms

to keep at arm’s length:  to avoid being connected to someone or something
I didn’t trust her, so I kept her at arm’s length.
on the tip of my tongue:  to be almost able to remember or expressed
His name was on the tip of my tongue, but I needed to ask him.

to pick someone’s brain:  to talk with someone to find out information from them
Jon is very good at math, so I picked his brain about a homework problem.
off the top of my head:  information offered quickly, without research or calculation
Off the top of my head, I remember 11 people on the guest list.
to cost an arm and a leg: to be very expensive
That shirt from Hermes costs an arm and a leg!
to stick one’s neck out: to take a risk
I stuck my neck out when I bought that antique rug. I hope it’s worth more money later on! 
get something off one’s chest: to tell someone your problems or frustrations
Thanks for listening to me complain about my brother. I needed to get it off my chest.
give someone a hand (with something):  to help someone
Can you give me a hand with this box? It’s too heavy to carry on my own.
keep your chin up: to try to stay positive when things seem negative
Keep your chin up! Things will get better soon.
like pulling teeth:  to be very difficult
Getting Bobby to clean his room is like pulling teeth.