If you don´t do X you shouldn´t do Y.
I should have done it.
I don´t think they should abolish Y.
Y should be turned off at all times during Z.
X shouldn’t do A without doing Y first.
They shouldn´t do away with Y.
Under no circumstances should Y be kept turned on during Z.
It was a mistake not to do it.
Don´t do Y unless you do X.
X must never do A without doing Y first.