There are several meanings but all quite similar. It could mean "let's give up" when you have tried to do something a couple of times and failed. Or "let's go home" when you complete a job or a task. You can also use this to try and end the argument when parties involved could not reach a compromise. Basically you use this to signify an ending of an event.

Let's wrap it up/Let's leave it at that/Let's put it to rest,