lose the thread

The phrase "lose the thread" is usually used metaphorically and refers to someone's inability to maintain a logical or coherent train of thought, argument, or conversation. It means that the person has become confused, lost focus, or no longer understands the main point or purpose of what they were saying or discussing. It suggests that the person has deviated from the main topic or failed to stay on track, making it difficult for others to follow and comprehend their viewpoint or message.