When I was pregnant, anyone I asked, and many people that I didn't ask, told me that having a child is both the best thing and the hardest thing that they have ever done. And that is exactly right! That is exactly how I would describe it. It strikes me that pretty much everyone describes it this way. It doesn't really tell you much though, and it leaves a parent-to-be looking for guidance, or a brand new parent looking for reassurance, a bit adrift. The description "it is the best and the hardest thing" seems like a nearly universally accurate way to describe having a child, but the particulars of why that is true, of how it is experienced, are very different for everyone. The particular way it is hard is different depending on who you are, and the particular way it is the best is probably different too. So I think we should try to expand on how it is the best and the hardest, even though it is hard to put into words. I've been on the other side of the question ...
Close the door. Write with no one looking over your shoulder. Don’t try to figure out what other people want to hear from you; figure out what you have to say. It’s the one and only thing you have to offer. ~ Barbara Kingsolver