More often than not, I have found that deep disappointment comes from holding very high expectations - of ourselves, of life, of those around us. Most of the time, those expectations are unrealistic.
For example, Petunia, you have a picture in your mind of what it should look like if your fiance is as excited about marrying you as you are about marrying him. He should "light up" when you walk in the room. Then, when you walk into the room and he doesn't light up the way you expect him to, you feel deflated. Your reaction is to interpret that as him not feeling as excited about getting married as you are, an assumption which is most probably completely and totally incorrect. Just because he doesn't fit your picture of how "excited" should look on him, doesn't mean he isn't feeling excited. He is his own person with his own way of processing and expressing his feelings. But you blame his "non-excitement" on his NRE and gf rather than looking at your expectations. Disappointment prevails and you start feeling jealousy, which is always a cover for other emotions we don't want to own up to.
You say, "He's trying to be what I need him to be, but his focus isn't really here with me." And you're disappointed. But until recently, it was okay for you to waffle about getting married and not be as on board as he was, right? Now that you turned it around, you "need him to be" in exactly the same place you are. I would hazard a guess that there's a part of you that really likes being in control, or in charge, probably because it gives you a sense of security (albeit a false one). It's kind of like being a little addicted to power. As long as the relationship was going along with the parameters you set, that was okay. You effectively controlled your fiance's behavior with your fears and insecurities, and now you feel more secure about marrying him and have flipped over to being okay with this or that thing that you weren't before, you want him to flip his attitude too. "Hey, I'm on board now, you get on board, too!" So now you're upset that he seems to be in a different place than you -- which does not meet your heavy expectations -- and you find yourself in turmoil, wrapped up in jealousy, and feeling powerless. You want things the way you want them, but he has a different process than you and is probably (understandably) being cautious and hesitant to get excited about anything because he got used to navigating around your insecurities.
You cannot work on him, or his gf. You can only work on yourself. If I were you, I would examine and deconstruct all your expectations.
You may find the following useful. It is from The Handbook to Higher Consciousness
, a classic on personal growth by Ken Keyes:
". . . no one has yet found happiness by using our emotion-backed desires as guides. Flashes of pleasure, yes. Happiness, no.
. . . Our wants and desires are so seductive. They masquerade as "needs" that must be satisfied so we can be happy at last. They lead from one illusion of happiness to another.
. . . We tell ourselves, "If only I could find the right person to love, then I would be happy." So we search for someone who our addictions tell us is the right person -- and we experience some pleasurable moments. But since we don't know how to love, the relationship gradually deteriorates. Then we decide we didn't have the right person after all! As we grow into higher consciousness, we discover that it is more important to be the right person than to find the right person.
We must deeply understand why all of our negative emotions are misleading guides to effective action in life situations. Our negative emotions are simply the result of an extensive pattern of scars and wounds we have experienced. . . . It saps your energy to be worried or anxious about a problem. Do what you can do but don't be addicted to the results or you will create more worry for yourself.
. . . as we reach physical maturity and our biocomputer (brain) is able to function more perceptively, we have all the power we need. But our biocomputer (backed up by the full repertory of our emotions) is still programmed to compensate for the power deficiency we experienced when we were infants and young children. We now need to learn to flow with the people and things around us. But our power addiction keeps us from loving people because we perceive them as objects that may threaten our power, prestige, or pecking order. If we want to love and be loved, we can't be addicted to power -- or to anything else.
As conscious beings, the only thing we need to find happiness in life is to perceive clearly who we are (not the social roles we are acting out), and exactly what are the real conditions, here and now, of our lives. How basically simple is our problem! But to achieve this clear perception of ourselves and the world around us takes constant inner work. And this means developing the habit of emotionally accepting whatever is here and now in our lives. For only an emotionally calm biocomputer can see clearly and wisely, and come up with effective ways to interact with people and situations."