The philosophical answers goes like this- When you have an expectation, you set yourself up. You can set them too high or too low. Rather than allowing marriage to unfold and be, we put expectations on marriage, as if we have some sort of control.
I am not even certain we can not have any expectations, but I have found expectations to be exceedingly challenging. For example, he says "I thought being married meant..." and follows up with something that sounds unreasonable to 50% of the world's population. "I just don't want to get hurt again," she says and we all know that is not realistic.
Being married means something different every year of marriage, every week and probably every day. Sure there are continuities, but expecting the future to look just like the past is a set up.
But then, how do you know what to expect? You don't. Neither with nor without expectations do we know what to expect. Live in the moment, be surprised and go with the flow. Be spontaneous- which essentially means we do not know what to expect. That is the joy of it. Stop trying to control the flow with your preferences, requirements, demands and expectations. They will not control the flow and likely you will have some negative feelings for not having gotten your way.
Let's be honest with one another on this. None of us really knows what to expect and this terrifies some people and others love it. If you are someone who likes order and control, the very notion of not knowing what to expect is disconcerting. Yet that is life. Just 'cause you expect something, does not mean it has to happen.
Take it a bit further and acknowledge that we all have preferences. There are ways I would like life to work out. When we really look at this deeply, we realize that our own personal preferences come from a limited view of the world. What I want may not actually be good for me. Do I still want to insist on my preference, then?
"I will only be happy when I get what I want," he said. I don't know about you, but I have had plenty of times when I got exactly what I wanted because I forced the issue and was more miserable than if I went with the flow and was spontaneous.
So what can I expect from marriage? Nothing with certainty. Well, except for change, death, hard work, some wonderful times, fun, arguing etc. I cannot control when I get these, so why do I grasp or try to control the outcome?
Good question. I don't have the answer for that. What did you expect?