The expression LOST CAUSE means a person or thing that is certain to fail:
You can apply for the job, but with your qualifications I think it’s a lost cause.
He’s a lost cause when it comes to talking to girls.
They consider the investment a lost cause, although some of them still believe in it.
I’ve been thinking and I realized we’ve been fighting for a lost cause.
This guy’s a lost cause. The sooner you break up the better for you.
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