Expressions used in Everyday Spoken English in Social and Professional contexts
If something is considered to be 'a lost cause', then it is believed to have a high chance of failing, or it is not worth pursuing. Likewise, if a person is 'a lost cause', they are considered to have no chance of succeeding. This can often be used to joke about someone who might not be doing what everyone expects of them. For example, if a man stops hanging out with his friends because his new girlfriend takes up all his time, his friends might say, "There's no point asking John to come out tonight. He spends all his time with his girlfriend. He's a lost cause!"