Motivation for getting good grades in graduate school Okay, so in grade school, in high school and also in college, a long face from my parents would scare me, so it would in most part act as an extra motivator for me to get good grades. In grad school though, I always have the option of getting a job and fending for myself. If I want to learn something, I always have MOOCs covering me up. I can have the education without constantly thinking of being admitted to a good school or dealing with social pressure. 

Now as I am into grad school, what specific points should I think of while studying? I really love studying, and enjoy the company of smart people; but sometimes I lose the extra impetus (which I used to get because of the fear of dealing with social embarrassment) in order to get good grades. Can someone just shed a different angle on the importance of getting good grades which does not include social stigma or the prospect of having a good job?
You are confusing cause and effect.  Good grades should never be a motivation for a truly good student (in graduate school or elsewhere).  Rather, good grades are a byproduct of engaging deeply with the material of a class.

When I was a graduate student, there were some classes that I was quite happy to get a B in, because they were far outside of my main area of work and taking them really stretched my mind; the B was a good reflection of the reality that I am not suited to be a theoretical mathematician, but that I had learned well from them regardless.  There were other classes that I would have been frankly ashamed to get anything other than an A in, because they were totally in my wheelhouse; if I had gotten even an A-, it would have reflected a real waste of my opportunity in that class.

In short: forget about grades in graduate school, except insofar as they are feedback on whether you are screwing up your education.