This is the 120th most frequent Serbian word.
своју
"Своју" means "one's own" (used for feminine singular objects in the accusative case).
Reflexive possessive pronoun "своју" relates to the subject "You" (implicit in 'мораш' meaning '(You) must').
Мораш да пазиш на своју књигу.
You must take care of your book.
Reflexive possessive pronoun "своју" refers to the subject 'Она' (She).
Она је заборавила своју ташну код куће.
She forgot her purse at home.
Reflexive possessive pronoun "своју" relates to the subject 'You' (plural or formal).