run out of steam
US /rʌn aʊt əv stiːm/
UK /rʌn aʊt əv stiːm/

1.
an Schwung verlieren, müde werden, die Puste ausgehen
to lose energy or enthusiasm and stop doing something, or to become tired and less effective
:
•
The project started strong, but it seems to be running out of steam now.
Das Projekt begann stark, aber es scheint jetzt an Schwung zu verlieren.
•
After working for ten hours, I started to run out of steam.
Nach zehn Stunden Arbeit begann ich, müde zu werden.