-고 말다: Ended Up Doing It — Regret or Relief

-고 말다 says the action finally came off — often after resistance, temptation, or delay. The feeling can be regret (I ended up…) or relief (I finally managed…).

Curriculum gloss: ended up doing it — usually regret, sometimes relief. 우리말샘 auxiliary 말다 in -고(야) 말다: the preceding action is finally realized, with positive or regretful stance.

Shape

참으려다 사고 말았어요.
비밀을 말하고 말았어요.
끝까지 버티고 말았어요.     relief / determination reading
울고 말았어요.
내고야 말았어요.

Emphatic cousin: -고야 말다.

Not -지 말다

Same Hangul stem 말다, opposite job:

사지 마세요.           don’t buy
사고 말았어요.         ended up buying

Mixing these is a classic intermediate trap.

Versus plain past and -고 나다

샀어요.                 fact
사고 말았어요.           fact + finally/against-will colour
사고 나서 후회했어요.     -고 나다: after buying, regretted

Versus -으려다가

-으려다가 abandons or redirects an intention. -고 말다 lets the action win:

참으려다가 말았어요.           stopped before buying (or shifted)
참으려다가 사고 말았어요.       tried to resist → bought anyway

Household evaluation talk

Impulse buys and product regrets love this auxiliary:

리뷰만 보려다 결제하고 말았어요.
중고로 하려다 새 제품을 고르고 말았어요.
아끼려다 결국 버리고 말았어요.

Quick checks

1. Verb + -고 말다 / -고야 말다.
2. Attitude matters — not bare past.
3. Never confuse with prohibition -지 말다.

Ask: did it finally happen, with regret or hard-won relief? If yes, -고 말다 fits.