run out of steam

/R AH1 N AW0 T AH0 V S T IY0 M/
verb
  1. 1

    To run out of energy or motivation.

    โ€œAfter climbing six flights of stairs she found she had run out of steam and had to sit down.โ€

Source: https://en.wiktionary.org/wiki/run%20out%20of%20steam