When negotiating, do you "lay your cards on the table"? Do you "beat around the bush"?
Try not to "cave in to" the other side.
See negotiation idioms here: http://www.idiomconnection.com/negotiations.html

Keep your cool / Keep your head (Idiom) - Remain calm in a difficult situation
http://idioms.thefreedictionary.com/keep+head

Idiom: Have broad shoulders
To have the ability to work hard and take on responsibilities and accept criticism (because you are strong with broad shoulders)
Source: http://www.idiomconnection.com/body.html