"i think this is upsetting them, let's stop it." - meaning to stop doing something that was being done "We've got to hand this assignment in tomorrow, let's finish it quickly." - meaning to complete something, reach an end point "This meeting's been going for a couple of hours now, let's leave it here." - meaning let's end this process here, maybe it's not the desired end that we had in mind, but let's just put a stop to it now Hope that helps!

Let’s finish it: “We haven’t finished our work, let’s finish it.” Let’s stop it: “Watch out for the skateboard. it's going down the hill. Let's stop it” Let’s leave it: “Why did we take that? That was bad idea. Let’s leave it.” ;) I hope I’ve helped