Pull yourself together
Definition 1 of 1
Pro Tip 1/3Emotional Recovery
Used when someone needs to overcome strong emotions and act more calmly. 
You've been crying for an hour, try to pull yourself together before the meeting.
Pro Tip 2/3Possible Impatience
Can imply frustration or impatience from the person asking for composure. 
We're all waiting for your decision, so pull yourself together and tell us.
Pro Tip 3/3Crisis Situations
Often used in urgent situations where calm is needed to handle a challenge. 
The situation was critical, but the captain managed to pull himself together and save the ship.