expression, ichidan verb
lose heart; lose motivation; be discouraged
Describes a drop in enthusiasm, spirit, or willpower, often after a setback or when something feels anticlimactic.
試合に負けて、すっかり気が抜けてしまった。
After losing the match, I completely lost heart.
目標
Once I achieved my goal, I lost motivation and don't feel like doing anything.
expression, ichidan verb
go flat; become stale; lose fizz
Used for carbonated drinks that lose their fizz, or more broadly for anything that loses its freshness or energy. The 'exhausted' nuance is an extension of this flatness.
炭酸飲料は開けたままにしておくと気が抜ける。
If you leave a carbonated drink open, it goes flat.
長い会議の後で、みんな気が抜けたようになっていた。
After the long meeting, everyone seemed drained.