The Mind Can’t Directly Process A Negative
Most people don't realize it but your mind can't directly process a negative.
Here's what I mean:
If someone says "Don't Forget To Vote", your mind drops off the word "Don't" and processes the rest of the sentence which says "Forget To Vote."
Then it adds the word "Don't"... but it's too late!
You mind has already absorbed the instruction of "Forget to Vote."
Which is unfortunately exactly the opposite of the real message you wanted to convey.
Here's What To Do Instead
Say what you DO what instead of what you don't want.
Rephrase your sentence to say what you want instead of what you don't want.
In this example, the new sentence would be "Remember to vote." It has the same meaning as "Don't forget to vote", but your unconcious mind is much more likely to absorb it the way it was intended.