"habits of thinking need not be for ever"

Question

Does this quote mean that we shuld not change our thinking habits or does it mean something else?

Answer 1

I think what it means that the way we think or the thoughts that we have today are not necessarily the same thoughts we will have in the future.  

Answer 2

It means you can change your thinking habits.  Ways of thinking are not set in stone.

Answer 3

It means that we should change our thinking habits.

"habits of thinking" meaning the way you think about something or an opinion

"need not be forever" meaning they do not have to remain the same.

You are capable of changing your mind and you are more than welcomed to do so.