They'll tell you not to do certain stuff:
Do not use colors, you are not good at it. Keep the colors to minimum!
Design is not like waiting under an apple tree and wait the apple to fall on you head for inspiration.
You cannot do this. It's not practical.
I see some of my friends are pinned down by those authority. They are weak-minded.
It is not the case whether the teachers are right or wrong, I don't believe there is absolute right or wrong, especially in field as ambiguous as design, it is the matter whether we understand the reason behind those comments or not.
In a way, if we took it literally, it seems that they are telling us what to do; but the true reason behind those comments is their concern on our grades. The teachers are worry that their students were unable to meet the deadline or that they will not do good.
The teachers wanted to ease their teaching as well as to protect us, the students, from mistakes.
This kind of teaching possess a very dangerous outcome of producing monotonic graduates, which it does each year with a few exceptional students, not more than 5%.
So what should we do as a student?
We should be aware of this issue. We should understand the reason behind those comments. It is crucial to do so, because once we are aware of this we can try not to get caught in this authority. We will not be pinned down even though we do as what we are taught to do.