This is one of those statements that just crushes me when I hear it spoken to a child. While it can be effective, let's take a moment to think about the way it can effect your child... Abandonment/Fear. How scary it must be for a two year old to think, if only for a moment, that their parent is going to leave them alone.
Dishonesty. Are you really going to leave your child alone? Unless you are actually going to leave your child alone (which is very sad as is) then this statement is filled with false promises.
This means that when you are trying to get out of your house in the morning, and your child won’t walk, and look at her and say, “Okay, I’m just going to leave without you.” you have both lied and created a sense of fear in her all in one short sentence. Yikes, I bet you didn't mean to do that!
Instead of using fear and lies to get a task done, give your child a choice. “You may walk to the car by yourself, or I will help you walk to the car, but we are leaving right now.” This puts your child in a position of control over their life by being given a choice. This also allows puts you in a position of control, because no matter what the answer is to that choice, you will both be leaving the house at the same time.