which part is wrong?
When a person finds itself in stressful situation, it helps to breath deeply.
Pronouns need to match their antecedents in person and number. What is the antecedent for "itself"? Which should be changed: the pronoun or the antecedent?
we can say
them self
"them self" is not correct English. Nor is would its corrected version work in this sentence.
"a person" = singular
"themselves" = plural
How will you fix the sentence?
The correct phrase would be: "When a person finds themselves in a stressful situation, it helps to breathe deeply."
The incorrect part in the original sentence is the use of "itself" to refer to a person. The pronoun "itself" is used when referring to a non-human or inanimate object. Since the subject of the sentence is a person, the correct pronoun to use is "themselves" to indicate that it refers to any gender.
To avoid this mistake, always remember to use "themselves" when referring to a person in a sentence.