You're a lifesaver.

KEY PHRASE
You're a lifesaver.
Strong informal thanks
A woman at an office desk looks relieved as a man hands her a phone charger, with laptops, papers, and coffee cups around them.
Maya
Oh no, my laptop is about to die before the meeting.
Daniel
Here, use my charger. I don't need it right now.
Maya
You're a lifesaver. Thank you so much.