Challenge
Write a letter to your past self.
It can be a letter to your one-week ago self, one-year ago self, or maybe even your childhood self. You can offer them advice, warnings, information, or even false reassurances -- whatever you'd like.
When you leave the apartment, remember to give them your new address. When you go to the park we used to go to, when you see them, talk to them, you'll regret it if you don't, it will stay on your mind forever.