Not at all, according to Steve Roesler at All Things Workplace. The statements are different, because our brains fail to register negatives.
When you use a negative sentence like, “Don’t forget the meeting time,” your brain ignores the “don’t” and only hears “forget the meeting time.”
If you get rid of the negativity and start using the positive alternative, saying “Remember the meeting time,” your coworkers will be more likely to show up on time.
The mind wants direction, not a sense of "lack." That's why it's important to pay attention to how you say things. If I tell you that something is "not very expensive" you'll focus on "expensive."
This is how improvement efforts often get bogged down: "I want us to make fewer mistakes" translates differently than "I want to increase the accuracy of our customer service solutions by 30% before November 30."
So, instead of telling you “Don’t forget to have a Happy Thanksgiving.” I’ll simply say, “have a Happy Thanksgiving!”