Throw in The Towel
This is a very common slang term used in spoken and written English.
The phrase originally comes from boxing. If a boxer is really hurt during a fight, their coaches and trainer might realize that they need to stop the fight because the boxer will get seriously hurt. They may suffer brain damage. The way to stop the fight in professional boxing is to throw the towel into the boxing ring.
In common spoken English, however, throwing in the towel just means to “quit” or “give up”.
Here are a couple of examples:
1.
I hate my job. I’m going to stay for a couple more weeks and if things don’t get any better I’m going to throw in the towel and look for a new job.
2.
My relationship isn’t going too well. My girlfriend and I always fight. I things don’t get better soon I think we might both agree to throw in the towel. (That means ‘break up” in this example)