Throw in the towel

ImageMeaning:

Give up doing something because it is too difficult to continue.

If you throw in the towel, you stop trying to do something because you have found that you won't succeed.

Example:

After discussing the matter with him for more than 3 hours, I threw in the towel and gave up persuading him.

There are still a few things you can do before throwing in the towel. Don't give up hope.