under one's own steam

prepositional phrase3

1. •
   Of the movement of a locomotive or a watercraft: by means of the power of its own engines (originally steam engines), rather than pulled or pushed by another vehicle.
2. •
   (figurative) Using one's own resources; independently, unaided.

   • "People come at their own risk, at their own expense, under their own steam," said Mhairi McKenzie-Robinson, chief administrator of the Fringe [Edinburgh Fringe Festival]. — 1987
3. •
   (figurative) At one's own initiative; of one's own accord, unbidden, unprompted.

   • I'd been wanting her to go for a long, long time, hoping she'd get up the gumption to do it under her own steam so I wouldn't have to make a scene about it. — 1980