"They're only truly great who are truly good."  

This statement is telling us to be good. People Judge you on who and what your character is. People will say you are truly great if you are truly good. Everyone has the potential to be truly great. But, they will only be considered great if they are only good.  For example, if you are great in school but not great at home or outside of school then you are not truly great. Because you will have to be a great person all the time not only at a specific place but everywhere. Another example is if you are good sometimes but not all the time. Then, you will not be considered great because, you are not good all the time. Finally,  if you are always good and always on your best behavior. Then that means that you are truly and truly a great person overall.