[acuity12]

The quote is a metaphor. It is clearly not about going the other way on lined paper, but rather the basic principle that one should not blindly follow instructions because someone else says they are right. If what you are told to do is wrong, don't do it.

[demallien]

Actually it's even stronger than that. There was no instruction to follow the line, it's just an assumption something that comes naturally which is why it is such a pernicious thing. The quote is a warning against having your thoughts and actions guided in a predetermined direction even without you being aware of it.