English Idioms and Phrases: Point of no return
When you reach 'point of no return' it is a point beyond which it is impossible to turn back or return to where you started. This could be for many reasons such as financial problems (ie too expensive) or physical limitations.
So for example once you sign a contract you reach the point of no return
"I have bought the house, I have signed the contract and now I can't go back" (I have reached the point of no return"
The origin of this phrase is to be found in aviation. The 'point of no return' or PNR is more commonly referred to by pilots as the 'radius of action formula' but it is 'point of no return' that has entered the English language as an idiom.
The PNR refers to a point of the flight when the plane no longer has enough fuel to return to the airstrip it originally came from, so that it has used more than half of its total fuel.
Therefore once the plane has gone past this point it cannot go back, thus the point of no return.
Cross the Rubicon, burn one's bridges (eg burn your bridges)