Even when a partner IS present, having them be your WHOLE life, the only person you want to hang out with, generally isn't healthy for you OR the quality and longevity of your relationship. And part of sharing your life with someone is having a life to share to begin with, which includes aspects in which they may sometimes be part of, but which are about you, not them: goals, your work, your hobbies, your friends and family, your own endeavors.

So, why not get started on those things? Not only are they essential in the first place, they're a fine way to get more comfortable with this separation, and to understand that in adult relationships, it's normal for both partners to have different lives which they share, rather than monopolize or live all siamese-twin-like.