"and drink water by measure..." drink the amount you need to live, "sleep on the ground" a person needs to sleep but he doesn't need a luxurious bed but rather spreads something on the ground and sleeps there this mishna has a few definitions, the simple definition is that this is the the simple meaning of the torah- that if you want to acquire torah- then this is what you need to do. but there's another understanding that the intention of our sages is to say-that you should be prepared, even for this. meaning- if you have a good bed to sleep on, so sleep- if you have a good meal to eat, so eat but don't turn it into a condition in order to progress in the service of g-d- and say if i have all the pleasures and comforts then i'm ok- i'll go to torah lectures, if not-i can't so it's saying: "this is the way of torah" if you want to acquire torah-be prepared even for salt and bread, water by measure, sleeping on the ground- a person who is prepared even for this, even when he has a bed to sleep on and a good meal to eat and he lives comfortably, he lives with the notion that this is not the purpose. because if it was up to me, i'd be willing to sleep on the floor, eat bread with water etc...because my goal in life is to advance myself in my spiritual work- and the main thing for me is torah.