My mother is sick to me: the possessive Serbian builds without a possessive
A Russian speaker reaching for possession reaches for у меня plus a genitive noun. Serbian's everyday equivalent skips both: the possessor turns into a bare dative clitic - ми, ти and му - clipped straight onto whatever is possessed, with no preposition anywhere in sight. Missing this one habit produces sentences that stay grammatical, get understood, and sound just slightly foreign every single time.