(something) is the straw that broke the camel's back

Something is the last thing experienced in a series of recurring offenses or problems that causes one to finally lose patience or for something to stop working. It alludes to the idea that a single additional piece of straw could cause an overladen camel to finally collapse. A: "Why are you getting upset about it now? Tom's been taking credit for your ideas for years." B: "Yeah, but him getting a promotion out of it is the straw that broke the camel's back!" I've hiked miles and miles in these boots—I can't believe they finally fell apart while I was walking in my own driveway! But I guess that was the straw that broke the camel's back. OK, that's the straw that broke the camel's back, kids! I told you to stop shouting back there, and now I'm turning this car around.