Rapunzel was in a tower for most of her life. Her first step out into the world was, interestingly enough, the outside world coming in--the prince. The second was the desert. She had the good and the bad, and, since it's a fairy tale, it worked out in the end.
Now, you're Rapunzel. Specifically, a Rapunzel who has been warned of the outside world, and also told some of the amazing things. The witch held up leaving the tower as one of the most important moments in your life, and explained that it will happen on this very specific date. That you have a tower filled with books, movies, songs all based around the various lands outside your tower. And it is very important that you keep up on your studies, because if you fall enough behind, you'll get stuck in the tower, and never learn of the land outside.
The prince smiles. He points out the time that can elapse between now and your leaving the tower. Then, he shows you exactly how little work you have to do to leave the tower, between now and then. All these things you've been doing just to leave the tower now barely matter. Because the date is set. Unless you actually try to get stuck here, he explains, you'll leave.
Your first feeling is probably simple glee. You've been working your whole life to reach this goal! There are so many wonderful, unbelievable things outside your tower!
And you're safe. For the first time in your life in nearly two decades, you don't have to bother. You get to leave on a schedule; you know when it's coming. And you're probably a touch restless. That may make you want to try new things: sneak out of the tower, or not study for tests, or stay up all night doing something frivolous. And there would be few or no negative consequences for doing so.
Then it strikes you, quite suddenly, that you may never have this opportunity again.
In that moment, the witch's warnings mean very little. That novel you wanted to pick up, the movie you wanted to stay up all night watching, the prince's touch, mean much.
You are free. You are old enough to be left alone to do things, and can shuck responsibilities without hurting people. You have been in the tower long enough to know this combination has not happened before, and know little enough of the world outside to not know if it will ever happen again.
Your future is set and planned for. Your past is done.
The prince's hand fits well in yours, and you live your next few months of moments in the present.