fight a losing battle
To continue to wage war when it is clear that one is not going to win.
adj
That loses or has lost.
Being on the losing team is disappointing.
noun
The process by which something is lost; a loss.
We conceive that an alternation of such losings and regainings will continue to be presented in England, until the whole business is set on a new and more stable basis by a revolution which shall not be moral only.