under (one's) own steam
On one's own; with no assistance from anyone else. The injured player was fortunately able to walk off the field under his own steam. Look, Mom, I can finish this book report under my own steam, OK? I don't need you hovering over me correcting my spelling!
under one's own steam
Independently, without help, as in For two years I published the quarterly newsletter under my own steam. This expression uses steam in the sense of "driving power," as in a steam engine. [Early 1900s]