This is one of those statements that crushes me when I hear it spoken to a child. Like, I can feel my spirit ache for the spirit of the child in this moment. While this statement can be effective, I want to challenge you to take a moment to think about two ways it will impact your child:

Fear
How scary it must be for a young child to think, if only for a moment, “My parent/caregiver is going to leave me. Abandon me.” And why? Because they did not want to leave a place of enjoyment? Or because they are naturally inclined to oppose you based on the development of their brain?
Lies.
Are you really going to leave your child alone? Are you seriously going to get in your car and drive away? Because unless you are actually going to leave your child then in this statement you are modeling acceptable dishonesty. Which is, in fact, HIGHLY unacceptable.

So what I am saying here is that when your child does not want to leave, and you are trying to get out of your house in the morning, or leave school at the end of the day and you say, “Okay, goodbye. I am leaving without you” you have simultaneously lied and created a sense of fear, all in one short sentence. Yikes, I bet you didn't mean to do that!

Instead of using fear and lies to get going, give your child a choice. “You may walk by yourself, or I will help you walk. We are leaving right now.” This choice puts your child in a position of much desired control over their life. This also puts you in a position of control, because no matter what the answer is, you will both be leaving the at the same time.

And if you establish this limit/expectation, I guarantee it will be more positive departures than negative ones. Once your child tests your limits a few times, of course. They are in the crisis of self-affirmation after all.