-어 버리다

V + 아/어 버리다 This indicates that an action has been completely finished, leaving nothing behind. It often conveys either relief from a burden or a sense of regret.

남자친구에게 돈을 다 줘 버렸어요.

I gave all my money away to my boyfriend.

어제는 잊어버리고 오늘을 살아요!

Forget about yesterday and live for today!

휴대폰을 잃어 버렸어요.

I lost my phone.

→ Especially with '잃다' (to lose), the form '잃어버렸다' sounds more natural and is used more frequently than the simple past '잃었다', which just indicates the state of having lost something.