Pull yourself up by your bootstraps
Improve your situation by your own efforts.
The origin of this descriptive phrase isn't known. It refers of course to boots and their straps (laces) and to the imagined feat of a lifting oneself off the ground by pulling on one's bootstraps. This impossible task is supposed to exemplify the achievement in getting out of a difficult situation by one's own efforts.
It was known by the early 20th century. James Joyce alluded to it in Ulysses, 1922:
"There were others who had forced their way to the top from the lowest rung by the aid of their bootstraps."
A more explicit use of the phrase comes a little later, from Kunitz & Haycraft's British Authors of the 19th Century:
"A poet who lifted himself by his own boot-straps from an obscure versifier to the ranks of real poetry."
Some early computers used a process called bootstrapping which alludes to this phrase. This involved loading a small amount of code which was then used to progressively load more complex code until the machine was ready for use. This has led to use of the term 'booting' to mean starting up a computer.