What is the following in red saying in the context?
Not everyone will want you to succeed. Jealousy and competition come with every innovation. The potential conflict that new ideas might bring contributes to the mental blocks that prevent people from creative thinking in the first place. "Don't stick your neck out" starts with "don't stick your mind out"---where you're not even looking for new ideas.
It's juste someone trying to be clever with word. It means something like:
'Don't try to be too adventurous/creative/original' means 'Don't even attempt to think in any way that is original or creative'.