What is hard about submission?
Well, if you're married to a good man who puts your needs on par with his own, who is responsible, and is loving-- not much.
But I have seen senarios on this board where men have spent more or less every dime who came into his posession and didn't take care of his wife and children's needs to the point they were in serious jeopordy. The OP's solution? Be more submissive and sign over her paycheck to him.
THAT'S what's so tough about submission. The abuse of it. The men who think it's a license to treat their wives like a child and order them around. Selfish men who don't feel good unless they've arranged their marriage and their household to serve their needs, to their liking, and not much else matters. Men who think women were put on earth to serve them and their children. It's that attitude of his wife not being an individual, but a service.
Now before it seems I'm ragging on men, the question concerned submission. Men have been given a tall order to love their wives, perhaps even more than she can love him. We could ask what's difficult about that? And it's the same thing: sometimes women make it impossible for their husbands to love them.
This is JMO, but I think Christians can spend too much time worrying about whether their marriage is submissive and putting that label on it. I've actually seen contests among women to see who can be the most submissive, who can serve her husband and children the most, who can be the least selfish and never care about herself. I think that competativeness is the nature of women, but, come on. If your marriage is working and healthy, I think there's a pretty good chance it's what God had in mind. My husband and I probably have a submissive marriage (he makes the decisions, but would argue that I hold all the power) but I don't think about it. I do what's right.