Взять себя в руки - Get ahold of oneself.

Взять - v. To take, to seize.--syn.брать
себя - (refl.) Myself, yourself, himself, herself, itself, ourselves, yourselves, themselves.
в(prp.) + винительный падеж => Into, to, in, a, per, at (a time),on (a day), <denotes pattern>,<express dimension>.
рука - n. Fem. Hand, arm.