Meaning/Usage: Used to tell someone to not give up; to be persistent; to not lose hope
Explanation: Another term that is often used is "hanging by a thread." In both phrases, the word "hang" is referring to holding to something. If you are holding on to a branch, then letting go indicates that you fall down and fail. Hanging by a thread is barely holding on. So when you tell someone to "hang in there," you are telling them to not let go and keep on fighting even though it is hard.