Conscious&Sub-conscious “Don’t Confuse them”

I read the a really fascinating excerpt from a book yesterday. It describes that the, sub-conscious can not understand words like”not”,”do not”,”can not” etc.
For example, when someone says, “do not imagine a blue elephant”, and you imagine a blue elephant immediately, Oor you yell at your child, ”do not run quickly”, he/she will run quickly immediately,either as wll. However, you should tell him/her “walk slower”to achieve your goal.
A psychologist may tell you “don’t be nervous” at the beginning of your therapy, but you will feel a little bit nervous, right? Instead if he says to you,”take it easy!”, you may feel a little bit more relaxed.
Like the title “Don not confuse ‘conscious’ and ‘sub-conscious’”, do you have the feeling you will confuse them? Let me know,haha!