personal affair; one's own affair
Refers to something that concerns oneself personally, often used when contrasting with others' matters.
Think about your own affairs first, rather than other people's.
He was happy for me as if it were his own affair.
我が事 is a more formal/classical way of saying 'one's own affair', contrasted with 人事 (ひとごと) meaning 'someone else's affair'.
Standard kanji spelling.
Mixed kanji-kana spelling; common in everyday writing.
Formed from 我が, the attributive form of 我, and 事 “matter; affair,” literally “one’s own affair.”