The difference is ...

Experience makes the difference.

The beginner, is not aware of their mistakes,

while others can notice them easily. 

The intermediate student, is aware of their mistakes,

and others can see the corrections they make.  

The advanced student, is aware of the mistakes that others do not see,

and when corrected only the teacher notices.  

The teacher, is aware of his mistakes unseen by others,

and makes corrections known only to himself.  

The Master, is aware that he still makes mistakes and strives to perfect them,

even though he knows perfection is impossible. 

Remember: "Honestly knowing where you stand at any given time, is one of the keys to moving forward in the right direction".