Passion in a relationship is chemical. Like oxytocin for women...
A good 180 for you to try would be to be stronger in the relationship. Try taking a more assertive stance??? I don't think this is something you tell her. You have to show it. Just saying these things is only going to make her think, "Yeah, right." You need to act it out. You might want to avoid relationship talk and just focus more on yourself. Becoming a more attractive guy. Think about some of the behaviors you had when you were dating. How have you changed? How might you become more like that guy you used to be?
There is no arriving, ever. It is all a continual becoming.