get a grip (on yourself)
US /ɡɛt ə ɡrɪp (ɒn jʊərˈsɛlf)/
UK /ɡɛt ə ɡrɪp (ɒn jʊərˈsɛlf)/

1.
to make an effort to control your emotions and behave more calmly
:
•
Come on, get a grip on yourself! There's no need to cry.
•
She needs to get a grip and stop panicking about the exam.