steam

full steam (or speed) ahead used to indicate that you should proceed with as much speed or energy as possible.

get up (or pick up) steam

1 generate enough pressure to drive a steam engine.

2 (of a project, plan, or process in its early stages) gradually gain more impetus and driving force.

have steam coming out of your ears be extremely angry or irritated. informal

let (or blow) off steam get rid of pent-up energy or emotion. informal

☞ The image here is of the release of excess steam from a steam engine through a valve.

run out of (or lose) steam lose impetus or enthusiasm. informal

1992Jeff TorringtonSwing Hammer Swing! Eventually I ran out of steam and came to a halt.

under your own steam without assistance from others.

1996Colin BatemanOf Wee Sweetie Mice & Men She was starting to move under her own steam, hesitant Bambi steps which weren't helped by being hurried along, but a good sign nevertheless.