The problem with marriage is that most people do not know how to create the boundary between reality and fairytale; they tend to go into marriage with all these expectations only to get hurt when reality sets in. This is due to the fact that realism is most definitely different from idealism and with all the mistake of taking weddings for marriages, planning and thinking once the wedding preparations go on well, all will be fine; reality is that after the wedding party and everybody has eaten rice with their souvenirs, everyone would go home and you are left to deal with the realities of marriage that might end up being too harsh for you to deal with.
When the honeymoon phase subsides, real work begins. While before marriage, there is always the showy affection and display of love; responsibilities of marriage come with requests that tend to overshadow these things. And with the amount of love that was going on before the marriage, it is expected that the partners feel they would never have a reason to quarrel or fight about anything. But getting to the house and living together means a different thing entirely, they could end up disagreeing over the tiniest things like why a spouse dropped shoes or bags where they dropped them. If there is not enough patience and maturity, these little things can alter the love of the marriage because at this point, irritation and anger begins to set in.
Also, in relation to planning for wedding and not marriage, when it comes to money, the couples tend to believe that once they have enough money for the event planner; that is the end of their problems. However, finances in marriage is quite deeper and larger than this. It is deeper than “the money for wedding is complete, we have an apartment, perhaps a car and we have clothes to wear” Sometimes, the problem begins when they realize that they do not get enough gifts from their spouse. Meanwhile, the spouse is looking beyond gifts and thinking about the future with kids. Sometimes, little problems like fixing the cars and fixing issues with the house has effect on the finances also.
In addition to this, before marriage, it is normal that so much time would be spent together that it would be totally normal. And people look forward to marriage just for the purpose of spending enough time with their spouse but the reality turns out to be that job would set in and eventually kids would start coming in and time spent together would be reduced. Meanwhile, this does not entirely mean the couples should not find how to spend time with each other, it just means that they might not be able to spend as much time with each other. Also, while the husband has only heard that women are cranky while pregnant and while menstruating, he gets to witness this live and this might have a toll on him.
The expectation with sex is entirely different. During the first stages of marriage, sex is always intense but over time, sparks will begin to fade. Stress would come in and sometimes hormones which might make the sex look forced or less interesting. Sometimes, sex would be interrupted or avoided totally which can create problems in the marriage if not dealt with. This is especially because the place of sex in marriages cannot be questioned and while different sex positions were planned before marriage, this might not be brought into realism.