How grown up you are shows when you are alone.
You’ve no doubt seen various quotes that say who you really are is who you are when no one is looking, or how moral you are is what you do when no one sees you. Along the same line, how grown up you are is most clearly demonstrated when no one else is around.
In marriage, this means (among other things) when your bride is not watching you do what you would do if she was watching. It means doing little acts of service when she won’t see you do it, and may not know you did it. It means not staring at the half naked women you pass on the the street when you are alone. It means talking kindly about your bride when she is not there to hear, and not saying nasty things about her eve when you are sure it won’t get back to you.
If who you are and how you act when she is around is different than when she is not around, then the “you” she sees is really not you, but a part you play to try to manipulate her.