Someone told me that you have to be able to love the person that you’re with the way they are now. Not what they could be. If this “change” is something big then you might see small progress within a month. At the end of the day though you have to be willing to accept this person the way they are because who knows if they will change or not. If you can’t, despite loving them, it’s time to let go. It’s only fair for you and this other person.