Imagine yourself in a place where you feel comfortable. Maybe you're sitting on a nice comfy couch? You might even be sipping on a delicious beverage. Eventually, you don't feel like getting up, even if you have something important to do or somewhere to go! That's the feeling that this expression is referring to. :)

Interesting expression. It means that you shouldn't let yourself feel "at home" or settle down, because this place will not be your home. You will have to leave soon.

Don't start anything new, or don't relax because there isn't enough time for that (as you are leaving soon). When used as a single sentence, it can also mean that you need to stay alert because something is going to happen.