To be a part of us, you have to give up a part of you. 
By us, I don’t mean you and me; I mean the generic us of any couple who want to make a commitment to each other. 
The part of you that you have to give up is the part that allows you to do whatever you want, whenever you want. 
That’s a lot of freedom to sacrifice on the altar of us. 
It is a bigger sacrifice for some than others. 
For those who only want to be with their partner, whatever and whenever, it’s no sacrifice at all.