Being a parent is hard (at least if you care about your children and their future). There is no way around it. There is no vacation. There are no days off. There are huge ups. There are huge downs. Some days our boys wake up super happy and ready to take on the world. Other days quite the opposite. There is no way to prepare yourself as there is no way to tell how they will be in the morning.
Our view is fairly simple - if you want to have children and be a parent then do it. Dive in head first and go to the max. If you are having children simply because other people want you to or you believe that it is what you should be doing then stop right there. You will not be happy and it will make being a parent so much more difficult that your children will feel it as well.
There are some people who will tell you how hard it is to be a parent and you cannot help but just laugh. (See example here). Everyone has a different definition of "hard work," but it is hard to have sympathy or empathy for a person who has unlimited resources to help with raising their children. That is not hard work.
Hard work is waking up at all hours of the night with your child when they are sick and getting up the next day and not slowing down. Hard work is getting up before dark in the morning to go to work so you can be home in time for dinner, bed and bath with your children then finishing your work after they are asleep. Hard work is making sure they have good habits and are polite and respectful. h
While it is definitely hard work, it is most definitely gratifying. In our home, everything we do is for our children. We would not have it any other way.